# One or more equations (two-by-two on different rows) with an enumerate to the left and the another on the right

Starting from these MWE into two links

1. How to place and number 3 short equations in one line? (Stefan Kottwitz's answer) with this MWE:

\documentclass[11pt,a4paper]{scrbook}
\usepackage{amsmath}
\usepackage{tabularx}
\begin{document}
\chapter{Equations}
See equations \eqref{eqn:1}, \eqref{eqn:2} and \eqref{eqn:3}.
\noindent\begin{tabularx}{\textwidth}{@{}XXX@{}}
$$x_{1} = \frac{A-A_{0}}{\frac{1}{2} \cdot \left( A_{\mathrm{A}} - A_{\mathrm{a}} \right)} \label{eqn:1}$$ &
$$x_{2} = \frac{B-B_{0}}{\frac{1}{2} \cdot \left( B_{\mathrm{A}} - B_{\mathrm{a}} \right)} \label{eqn:2}$$ &
$$x_{3} = \frac{C-C_{0}}{\frac{1}{2} \cdot \left( C_{\mathrm{A}} - C_{\mathrm{a}} \right)} \label{eqn:3}$$
\end{tabularx}
\end{document}

1. My previous question An elegant aspect for enumerate the equations of a book (Werner's answer) that that I have modified a bit,

\documentclass{book}
\usepackage[top=2.5cm,bottom=2.2cm,
a4paper]{geometry}  %%%%%%%%%%% <--------- added
\usepackage{mathtools,amssymb}
\usepackage[svgnames, dvipsnames, table, x11names]{xcolor}
\usepackage{pifont}
\usepackage{tabularx} %%%%%%%%%%% <--------- added
\definecolor{ocre}{RGB}{243,102,25}
\usepackage{lipsum} %%%%%%%%%%% <--------- added

%----------------------------------------------------------------------------------
%   Change number equations with sections
%----------------------------------------------------------------------------------
\usepackage{chngcntr}
\counterwithin{equation}{section}

\renewcommand{\theequation}{\thesection-\arabic{equation}}
\newcommand{\eqnnumsymbol}{\textcolor{ocre}{\reflectbox{\ding{228}}}}

\makeatletter
\newtagform{bbrackets}% <name>
[\textbf]% Internal style
{(}% Left bracket
{\ifnum\pdfstrcmp{\@currenvir}{equation}=0
\eqnnumsymbol%
\else
\ifnum\pdfstrcmp{\@currenvir}{align}=0
\eqnnumsymbol%
\fi
\fi
)}% Right bracket
\makeatother
\usetagform{bbrackets}

\begin{document}
\lipsum[3][1-7]

\begin{tabularx}{\textwidth}{@{}XXX@{}}
$$f(x + y) = f(x) + f(y), \label{eqn:1}$$ &
$$f(ax) = af(x),\, x,y\in V, a\in\mathbb{C} \label{eqn:2}$$
\end{tabularx}

\lipsum[2][1-4]

\end{document}


we observe that the enumeration in the same line goes out the margins. See (out with red arrows in the image). However, I would like something of this type that I have modified with paint for clarity of my question:

This possible output, however, must be achieved realized when two or more equations (with two-by-two equations on different rows).

Please, what are the possible solutions?

• Add \noindent before \begin{tabularx}. (As it is already present in the first example cde in your question.) Commented Aug 11, 2019 at 20:53
• @leandriis Kindest. Hi, I thought it wouldn't help \noindent. The first one is solved. +1 for all. Commented Aug 11, 2019 at 21:05
• Suppose you have three equations on the same line. If I understand well, the leftmost equation should be numbered in its left, the rightmost on its right. But where should be placed the number of the middle equation? Commented Aug 11, 2019 at 21:22
• @Bernard Your comment is perfect. The equations must be two-by-two on same line. Commented Aug 11, 2019 at 21:25
• see, if tex.stackexchange.com/questions/467784/… gives solution which you looking for. Commented Aug 11, 2019 at 22:34

I propose this (based on my solution to your previous question). Note you have to use an amsmath environment, i.e. replace equation with gather for instance.

\documentclass{book}
\usepackage[top=2.5cm,bottom=2.2cm,
a4paper]{geometry} %%%%%%%%%%% <--------- added
\usepackage{mathtools,amssymb}
\usepackage[svgnames, dvipsnames, table, x11names]{xcolor}
\usepackage{pifont}
\usepackage{tabularx} %%%%%%%%%%% <--------- added
\definecolor{ocre}{RGB}{243,102,25}
\usepackage{lipsum} %%%%%%%%%%% <--------- added

%----------------------------------------------------------------------------------
% Change number equations with sections
%----------------------------------------------------------------------------------
\usepackage{chngcntr}
\counterwithin{equation}{section}

\renewcommand{\theequation}{\thesection-\arabic{equation}}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\newcommand{\leqnomode}{\tagsleft@true\usetagform{larrowtip}}
\newcommand{\reqnomode}{\tagsleft@false}
\newcommand*{\compress}{\@minipagetrue}
\newcommand*{\depress}{\@minipagefalse}
\makeatother

\usepackage{nccmath}
\usetagform{arrowtip}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\begin{document}

\lipsum[3][1-7]

{\noindent\begin{tabularx}{\textwidth}{@{}>{\compress\leqnomode}X<{\depress}>{\compress}X <{\depress}@{}}
\begin{gather}
f(x + y) = f(x) + f(y),
\label{eqn:1}
\end{gather} &
\begin{gather}
f(ax) = af(x),\,
x,y\in V, a\in\mathbb{C}
\label{eqn:2}
\end{gather}
\end{tabularx}}

\lipsum[2][1-4]

\begin{gather}
f(x + y) = f(x) + f(y),
\label{eqn:1}
\end{gather}

\leqnomode
\begin{gather}
f(ax) = af(x),\,
x,y\in V, a\in\mathbb{C}
\label{eqn:2}
\end{gather}

\end{document}


• Excellent. Please, can you put into your code the part that have you added with %%%%%%%% <--------- added? Thus I confronted everything with my book code. Thank you very much. Commented Aug 12, 2019 at 7:00
• Done. As there already were older  <-------- added from your code, I wrote %%% Added on a separate line. The table preamble has changed too. Maybe it might be worth defining a new column type, say \renewcommand{\tabularxcolumn}[1]{>{\compress}p{#1}<{\depress}}\newcolumntype{E}{>{\leqnomode}X}. Commented Aug 12, 2019 at 9:27
• Thank you very much for all and....for your MWE. Commented Aug 12, 2019 at 10:21