%% An UIT Edition example

%%
%% An UIT Edition example
%%
%% Example 08-03-12 on page 163.
%%
%% 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{153.70511pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands
\def\yPh{\vphantom{y}}
\let\ul\underline
\StopShownPreambleCommands
\begin{document}
$\underline{x}+\underline{y}=\underline{z}$\\[8pt]
$ \ul{x\yPh} + \ul{y} = \ul{z\yPh} $\\[8pt]
$ \ul{x_1} + \ul{y_2} = \ul{z_3} $
\end{document}