# how to solve numbering problem of a latex equation?

I have a question please, my code is the following:

\documentclass{amsart}
\usepackage{amssymb}
\usepackage{hyperref}
%======== Outils linguistiques ===

\usepackage[utf8]{inputenc}
\usepackage[french]{babel}
\usepackage{lmodern}
%======== Mathematiques ==========

\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage{amsthm}
%======== Mise en forme du texte =====

\usepackage{ulem}
%\usepackage{soul}
\usepackage{setspace}% espace entre les lignes
%\onehalfspace
%\doublespace

%\usepackage[Lenny]{fncychap} % Lenny, Conny ,Bjarne, Rejne, Glenn, Sonny
%======== Marges ===============

\usepackage[left=2.5cm,right=2.5cm,top=2cm,bottom=2cm]{geometry}

\usepackage{fancybox}
\usepackage{framed}
%===== Les couleurs ===========

\usepackage{color,xcolor}
%======= entêtes et bas de page ======

\usepackage{fancyhdr}
\usepackage{lastpage}
\pagestyle{fancy}
\lfoot{ }
\cfoot{Page \thepage\ sur \pageref{LastPage}}
\renewcommand{\footrulewidth}{1pt}
%===== Les theoremes ============

%\usepackage[framed]{ntheorem}
\newtheoremstyle{break}% name
{\topsep}%   Space above, empty = usual value'
{\topsep}%   Space below
{\itshape}%  Body font
{}%          Indent amount (empty = no indent, \parindent = para indent)
{\newline}%  Space after thm head: \newline = linebreak

%% This has a default type size 10pt.  Other options are 11pt and 12pt
%% This are set by replacing the command above by
%% \documentclass[11pt]{amsart}
%%
%% or
%%
%% \documentclass[12pt]{amsart}
%%
%%
%% Some mathematical symbols are not included in the basic LaTeX
%% package.  Uncommenting the following makes more commands
%% available.
%%

%\usepackage{amssymb}

%%
%% The following is commands are used for importing various types of
%% grapics.
%%

%\usepackage{epsfig}        % For postscript
%\usepackage{epic,eepic}       % For epic and eepic output from xfig

%%
%% The following is very useful in keeping track of labels while
%% writing.  The variant   \usepackage[notcite]{showkeys}
%% does not show the labels on the \cite commands.
%%

%\usepackageshowkeys}

%%%%
%%%% The next few commands set up the theorem type environments.
%%%% Here they are set up to be numbered section.number, but this can
%%%% be changed.
%%%%

\newtheorem{lem}{Lemma}[section]
\newtheorem{cor}{Corollary}[section]
\newtheorem{thm}{Theorem}[section]
\newtheorem{prop}{Proposition}[section]
\newtheorem{df}{Definition}[section]
\newtheorem{rmq}{Remark}[section]
\newtheorem{pro}{Proof}[section]

%%
%% If some other type is need, say conjectures, then it is constructed
%% by editing and uncommenting the following.
%%

%\newtheorem{conj}[thm]{Conjecture}

%%%
%%% The following gives definition type environments (which only differ
%%% from theorem type invironmants in the choices of fonts).  The
%%% numbering is still tied to the theorem counter.
%%%

\theoremstyle{definition}
\newtheorem{definition}[thm]{Definition}
\newtheorem{example}[thm]{Example}
%\newtheorem{remark}[Rmk]{Remark}

%%
%% Again more of these can be added by uncommenting and editing the
%% following.
%%

%\newtheorem{note}[thm]{Note}

%%%
%%% The following gives remark type environments (which only differ
%%% from theorem type invironmants in the choices of fonts).  The
%%% numbering is still tied to the theorem counter.
%%%

\theoremstyle{remark}

\newtheorem{remark}[rmq]{Remark}

%%%
%%% The following, if uncommented, numbers equations within sections.
%%%

\numberwithin{equation}{section}

%%%
%%% The following show how to make definition (also called macros or
%%% abbreviations).  For example to use get a bold face R for use to
%%% name the real numbers the command is \mathbf{R}.  To save typing we
%%% can abbreviate as

\newcommand{\N}{\mathbb{N}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\C}{\mathbb{C}}
\newcommand{\K}{\mathbb{K}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\F}{\mathbb{F}}
\newcommand{\LL}{\mathbb{L}}

%%
%% The comment after the defintion is not required, but if you are
%% working with someone they will likely thank you for explaining your
%% definition.
%%
%% Now add you own definitions:
%%

%%%
%%% Mathematical operators (things like sin and cos which are used as
%%% functions and have slightly different spacing when typeset than
%%% variables are defined as follows:
%%%

\DeclareMathOperator{\dist}{dist} % The distance.

%%
%% This is the end of the preamble.
%%

\begin{document}

%%
%% The title of the paper goes here.  Edit to your title.
%%

\title{xxxxxxxxxxxxxxxxxxxxxxxxxx}

%%
%%

\author{xxxxxxxxxxxxxxxxx}
\email{Email}
%\urladdr{www.math.sc.edu/$\sim$howard} % Delete if not wanted.

%%
%% If there is another author uncomment and edit the following.
%%

%\author{Second Author}
%\address{Department of Mathematics, University of ***,}
%\email{email****}
%\urladdr{www.math.sc.edu/$\sim$second}

%\author{Third Author}
%\address{Department of Mathematics, University of ***,}
%\email{email****}
%% If there are three of more authors they are added in the obvious
%% way.
%%

%%%
%%% The following is for the abstract.  The abstract is optional and
%%% if not used just delete, or comment out, the following.
%%%

\begin{abstract}

............xxxxxxxxxxxx...........

\end{abstract}

%%
%%  LaTeX will not make the title for the paper unless told to do so.
%%  This is done by uncommenting the following.
%%

\maketitle

%%
%% uncommenting the following:
%%

\tableofcontents

%%
%%  To enter text is easy.  Just type it.  A blank line starts a new
%%  paragraph.
%%
\section{Introduction}
....xxxxxxx........
\setlength{\parskip}{0.1mm}
These systems are expressed as follows\\
\\
$$\label{S1} \left\{ \begin{array}{lll} X^{\prime}(t) &=& f(t,X(t))\quad t_{0}<t<t_{n+1}=T, t \neq t_{k},\\ \bigtriangleup X(t_{k})&=& I_{k}(X(t_{k}))\quad k \in \theta_{m}^{n},\\ X(t_{0})&=& X_{0}.\;\;\; \end{array} \right.$$

$$\begin{cases} \dfrac{d u(t)}{dt}=Au(t)+f(t),\; t\in ]0,T[\\ u(0)=x\in X. \end{cases} \label{1}$$

\end{document}


As you can see the numbering of my equation is behind the equation, I want that number (1.1) to be after the equation and not before! can anyone help please?

• Welcome to TeX.SX! We need to see your code as it's impossible to guess what is going wrong if we don't know what you are doing! Please do not post your full code but instead distill it down to a minimal working example. This should compile and be as small as possible to demonstrate your problem. – user30471 Jun 16 '20 at 23:45

As for the updated question, you need to use

  \documentclass[reqno]{amsart}


instead of \documentclass{amsart}.

\documentclass[reqno]{amsart}
\usepackage{amssymb}
\usepackage{hyperref}
%======== Outils linguistiques ===

\usepackage[utf8]{inputenc}
\usepackage[french]{babel}
\usepackage{lmodern}
%======== Mathematiques ==========

\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage{amsthm}
%======== Mise en forme du texte =====

\usepackage{ulem}
%\usepackage{soul}
\usepackage{setspace}% espace entre les lignes
%\onehalfspace
%\doublespace

%\usepackage[Lenny]{fncychap} % Lenny, Conny ,Bjarne, Rejne, Glenn, Sonny
%======== Marges ===============

\usepackage[left=2.5cm,right=2.5cm,top=2cm,bottom=2cm]{geometry}

\usepackage{fancybox}
\usepackage{framed}
%===== Les couleurs ===========

\usepackage{color,xcolor}
%======= entêtes et bas de page ======

\usepackage{fancyhdr}
\usepackage{lastpage}
\pagestyle{fancy}
\lfoot{ }
\cfoot{Page \thepage\ sur \pageref{LastPage}}
\renewcommand{\footrulewidth}{1pt}
%===== Les theoremes ============

%\usepackage[framed]{ntheorem}
\newtheoremstyle{break}% name
{\topsep}%   Space above, empty = usual value'
{\topsep}%   Space below
{\itshape}%  Body font
{}%          Indent amount (empty = no indent, \parindent = para indent)
{\newline}%  Space after thm head: \newline = linebreak

%% This has a default type size 10pt.  Other options are 11pt and 12pt
%% This are set by replacing the command above by
%% \documentclass[11pt]{amsart}
%%
%% or
%%
%% \documentclass[12pt]{amsart}
%%
%%
%% Some mathematical symbols are not included in the basic LaTeX
%% package.  Uncommenting the following makes more commands
%% available.
%%

%\usepackage{amssymb}

%%
%% The following is commands are used for importing various types of
%% grapics.
%%

%\usepackage{epsfig}        % For postscript
%\usepackage{epic,eepic}       % For epic and eepic output from xfig

%%
%% The following is very useful in keeping track of labels while
%% writing.  The variant   \usepackage[notcite]{showkeys}
%% does not show the labels on the \cite commands.
%%

%\usepackageshowkeys}

%%%%
%%%% The next few commands set up the theorem type environments.
%%%% Here they are set up to be numbered section.number, but this can
%%%% be changed.
%%%%

\newtheorem{lem}{Lemma}[section]
\newtheorem{cor}{Corollary}[section]
\newtheorem{thm}{Theorem}[section]
\newtheorem{prop}{Proposition}[section]
\newtheorem{df}{Definition}[section]
\newtheorem{rmq}{Remark}[section]
\newtheorem{pro}{Proof}[section]

%%
%% If some other type is need, say conjectures, then it is constructed
%% by editing and uncommenting the following.
%%

%\newtheorem{conj}[thm]{Conjecture}

%%%
%%% The following gives definition type environments (which only differ
%%% from theorem type invironmants in the choices of fonts).  The
%%% numbering is still tied to the theorem counter.
%%%

\theoremstyle{definition}
\newtheorem{definition}[thm]{Definition}
\newtheorem{example}[thm]{Example}
%\newtheorem{remark}[Rmk]{Remark}

%%
%% Again more of these can be added by uncommenting and editing the
%% following.
%%

%\newtheorem{note}[thm]{Note}

%%%
%%% The following gives remark type environments (which only differ
%%% from theorem type invironmants in the choices of fonts).  The
%%% numbering is still tied to the theorem counter.
%%%

\theoremstyle{remark}

\newtheorem{remark}[rmq]{Remark}

%%%
%%% The following, if uncommented, numbers equations within sections.
%%%

\numberwithin{equation}{section}

%%%
%%% The following show how to make definition (also called macros or
%%% abbreviations).  For example to use get a bold face R for use to
%%% name the real numbers the command is \mathbf{R}.  To save typing we
%%% can abbreviate as

\newcommand{\N}{\mathbb{N}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\C}{\mathbb{C}}
\newcommand{\K}{\mathbb{K}}
\newcommand{\Z}{\mathbb{Z}}
\newcommand{\F}{\mathbb{F}}
\newcommand{\LL}{\mathbb{L}}
\newcommand{\diff}{\mathop{}\!\mathrm{d}}

%%
%% The comment after the defintion is not required, but if you are
%% working with someone they will likely thank you for explaining your
%% definition.
%%
%% Now add you own definitions:
%%

%%%
%%% Mathematical operators (things like sin and cos which are used as
%%% functions and have slightly different spacing when typeset than
%%% variables are defined as follows:
%%%

\DeclareMathOperator{\dist}{dist} % The distance.

%%
%% This is the end of the preamble.
%%

\begin{document}

%%
%% The title of the paper goes here.  Edit to your title.
%%

\title{xxxxxxxxxxxxxxxxxxxxxxxxxx}

%%
%%

\author{xxxxxxxxxxxxxxxxx}
\email{Email}
%\urladdr{www.math.sc.edu/$\sim$howard} % Delete if not wanted.

%%
%% If there is another author uncomment and edit the following.
%%

%\author{Second Author}
%\address{Department of Mathematics, University of ***,}
%\email{email****}
%\urladdr{www.math.sc.edu/$\sim$second}

%\author{Third Author}
%\address{Department of Mathematics, University of ***,}
%\email{email****}
%% If there are three of more authors they are added in the obvious
%% way.
%%

%%%
%%% The following is for the abstract.  The abstract is optional and
%%% if not used just delete, or comment out, the following.
%%%

\begin{abstract}

............xxxxxxxxxxxx...........

\end{abstract}

%%
%%  LaTeX will not make the title for the paper unless told to do so.
%%  This is done by uncommenting the following.
%%

\maketitle

%%
%% uncommenting the following:
%%

\tableofcontents

%%
%%  To enter text is easy.  Just type it.  A blank line starts a new
%%  paragraph.
%%
\setlength{\parskip}{0.1mm}

\section{Introduction}
....xxxxxxx........

These systems are expressed as follows
\label{S1} \left\lbrace\begin{aligned} X^{\prime}(t) &= f(t,X(t))\quad t_{0}<t<t_{n+1}=T, t \neq t_{k}\;,\\ \bigtriangleup X(t_{k})&= I_{k}(X(t_{k}))\quad k \in \theta_{m}^{n}\;,\\ X(t_{0})&= X_{0}\;. \end{aligned} \right.

\left\lbrace\begin{aligned} \dfrac{\diff u(t)}{\diff t} &=Au(t)+f(t)\;,\quad t\in ]0,T[\\ u(0)&=x\in X. \end{aligned} \right. \label{1}

or

These systems are expressed as follows
\label{S1'} \left.\begin{aligned} X^{\prime}(t) &= f(t,X(t))\quad t_{0}<t<t_{n+1}=T, t \neq t_{k}\\\ \bigtriangleup X(t_{k})&= I_{k}(X(t_{k}))\quad k \in \theta_{m}^{n}\\ X(t_{0})&= X_{0} \end{aligned} \right\rbrace

\left.\begin{aligned} \dfrac{\diff u(t)}{\diff t} &=Au(t)+f(t)\;,\quad t\in ]0,T[\\ u(0)&=x\in X. \end{aligned} \right\rbrace \label{1}

\end{document}


ANSWER TO THE ORIGINAL QUESTION: The leqno option is what you are probably looking for.

\documentclass{article}
\usepackage[leqno]{amsmath}
\numberwithin{equation}{section}
\begin{document}
\section{Some section}
\left\lbrace\begin{aligned} X'(t)&=f\bigl(t,X(t)\bigr)\quad\dots\\ U&=V\\ X&=Y \end{aligned}\right.
\end{document}


As you see, I had not the patience to reconstruct the equation from a screen shot. Also I prefer the alignment that comes with align or aligned over some centered stuff.

One can also use empheq etc., this post is only to mention leqno.

• I think my question was not clear enough, Firstly the code I used is the following: – walid fssm Jun 17 '20 at 13:32
• @walidfssm In your document, replace \document-class{amsart} by \documentclass[reqno]{amsart}. – user194703 Jun 17 '20 at 13:56
• thank you so much, It's working very well. @Schrödinger's cat – walid fssm Jun 17 '20 at 14:11

By default the amsart class sets the option leqno.

Use reqno.

\documentclass[reqno]{amsart}

[...all the same...]

\section{Introduction}
....xxxxxxx........
These systems are expressed as follows
\begin{gather}
\label{S1}
\begin{cases}
\begin{aligned}
X^{\prime}(t) &= f(t,X(t))\quad t_{0}<t<t_{n+1}=T, t \neq t_{k},\\
\bigtriangleup X(t_{k})&= I_{k}(X(t_{k}))\quad k \in \theta_{m}^{n},\\
X(t_{0})&= X_{0}.
\end{aligned}
\end{cases}
\\
\label{1}
\begin{cases}
\dfrac{d u(t)}{dt}=Au(t)+f(t),\; t\in \mathopen]0,T\mathclose[\\
u(0)=x\in X.
\end{cases}
\end{gather}

\end{document}


I made a few fixes to your code. Never use \\ to end lines in normal text and certainly not for “leaving a blank line”. Consecutive displays should not be in separate equation environments.

You may want to align the braces, which can be obtained as follows:

\section{Introduction}
....xxxxxxx........
These systems are expressed as follows
\begin{align}
\label{S1}
&\begin{cases}
\begin{aligned}
X^{\prime}(t) &= f(t,X(t))\quad t_{0}<t<t_{n+1}=T, t \neq t_{k},\\
\bigtriangleup X(t_{k})&= I_{k}(X(t_{k}))\quad k \in \theta_{m}^{n},\\
X(t_{0})&= X_{0}.
\end{aligned}
\end{cases}
\\
\label{1}
&\begin{cases}
\dfrac{d u(t)}{dt}=Au(t)+f(t),\; t\in \mathopen]0,T\mathclose[\\
u(0)=x\in X.
\end{cases}
\end{align}


• @egreg thank you, It's working – walid fssm Jun 17 '20 at 14:13