%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  2. Auflage
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%%  Beispiel 09-07-21 auf Seite 425.
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%%  Copyright (C) 2016 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
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\AtBeginDocument{\setlength\parindent{0pt}}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{align*}
\begin{split}
   \framebox[0.25\columnwidth]{x}\\
   \framebox[0.45\columnwidth]{x}\\
   \framebox[0.75\columnwidth]{x}\\
   \framebox[\columnwidth]{x}
\end{split}
\end{align*}
\end{document}
