# Equation tag alignment inside enumerate

I am trying to align my tag to left margin. I've seen this answer, but it did not help me muh as I don't want to change the class to ams. I have a solution (the code below), but I wonder if there is a better, wiser way to achieve the same. I would be happy if all displayed-math environments ignored all the indents added by enumerate or itemize.

\documentclass[11pt,leqno]{article}
\usepackage{amsmath,amssymb,enumerate}
\begin{document}
\item
Suppose $n=\sum_{p\in\bar{P}(n)}F_p$. We will show that\\
\hspace*{-1.4cm}\parbox{\textwidth}{
$$\bar{P}(n)=P\left(n-F_{p_n}\right)\cup\{p_n\},\label{fpn}$$}
\end{enumerate}
\end{document}

• Preferable here use \hspace*{-\leftmargin} rather then \hspace*{-1.4cm}. Aug 15 '15 at 21:03

Maybe you find the following approach useful:

\documentclass[11pt,leqno]{article}
\usepackage{amsmath,amssymb,enumerate}
\usepackage{calc,changepage}
\usepackage{lipsum}
\newenvironment{textwide}% environment for display math in lists
\vspace{-1em}

\begin{document}
\lipsum[2]
Suppose $n=\sum_{p\in\bar{P}(n)}F_p$. We will show that
$$\bar{P}(n)=P\left(n-F_{p_n}\right)\cup\{p_n\},\label{fpn}$$