%% 
%%  An UIT Edition example
%% 
%%  Example 06-02-20 on page 87.
%% 
%%  Copyright (C) 2010 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{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\begin{flalign*}
                                         && 12(x-1)+20(y-3)+14(z-2) &= 0\\
\text{expand and transpose} &&  6x+10y+7z-50 &= 0
\end{flalign*}
\end{document}