%% 
%%  Die DANTE-Edition
%%  Ein Beispiel der LaTeX Referenz
%%  3. Auflage
%% 
%% 
%%  Copyright (C) 2013 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
%StartShownPreambleCommands
\usepackage{amsmath,setspace}
\newcommand*\fBox[2][0.125]{\framebox[#1\columnwidth]{#2}}
\setstretch{0.5}
%StopShownPreambleCommands
\begin{document}
\begin{align*}
\fBox{align*} &= \fBox{x} & \fBox{x}&= \fBox{x}\\
\fBox{align*} &= \fBox{x} & \fBox{x} &= \fBox{x}
\end{align*}
%
\begin{alignat*}{2}
\fBox{alignat*} &= \fBox{x} & \fBox{x} &= \fBox{x}\\
\fBox{alignat*} &= \fBox{x} & \fBox{x} &= \fBox{x}
\end{alignat*}
%
\begin{flalign*}
\fBox{flalign*} &= \fBox{x} & \fBox{x} &= \fBox{x}\\
\fBox{flalign*} &= \fBox{x} & \fBox{x} &= \fBox{x}
\end{flalign*}
\end{document}