%% 
%%  Example 03-03-8 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}

%StartShownPreambleCommands

%StopShownPreambleCommands
\begin{document}
$ {a\over b} \qquad
  {{m\over n}\over{a+b}} $
\[ {m\over n}\over{a+b} \]
\end{document}
