%% 
%%  Example 01-11-4 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\usepackage[T1]{fontenc}
\usepackage{kpfonts}
%StartShownPreambleCommands
\usepackage{amsmath}% for align
%StopShownPreambleCommands
\begin{document}
\begin{minipage}[t]{0.3\linewidth}
\begin{align*}
  y &= d\\
  y &= c\frac{1}{x}+d\\
  y &= b\frac{1}{x^{2}%
                \rlap{\hspace{-1cm}\rule{10cm}{0.4pt}}}+cx+d\\% \rlap only demo
\end{align*}
\end{minipage}\hfill
\begin{minipage}[t]{0.3\linewidth}
\setlength\jot{0pt}
\begin{align*}
  y &= d\\ y &= c\frac{1}{x}+d\\ y &= b\frac{1}{x^{2}}+cx+d\\
\end{align*}
\end{minipage}\hfill
\begin{minipage}[t]{0.3\linewidth}
\setlength\jot{10pt}
\begin{align*}
  y &= d\\ y &= c\frac{1}{x}+d\\ y &= b\frac{1}{x^{2}}+cx+d\\
\end{align*}
\end{minipage}
\end{document}
