%% 
%%  Example 07-07-2 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
\usepackage[T1]{fontenc}
%StartShownPreambleCommands
\usepackage{amsmath}
\newcommand\x{blah blah blah blah blah blah blah blah }
\addtolength\abovedisplayshortskip{-.5cm}% decrease the skip
\addtolength\abovedisplayskip{-.5cm}
%StopShownPreambleCommands
\begin{document}
\rule{\columnwidth}{1pt}
\x\x\x
\begin{align}
\hphantom{\mbox{$f(x)-g(x)$}} & \hphantom{\mbox{$= x^2+x^3+x^4+x^5+b$}}\nonumber\\
f(x) &= a\\
g(x) &= x^2-4x
\end{align}
%
\x\x\x
\begin{align}
\hphantom{\mbox{$f(x)-g(x)$}} & \hphantom{\mbox{$= x^2+x^3+x^4+x^5+b$}}\nonumber\\
f(x)-g(x) &= x^2+x^3+x
\end{align}
\x\x\x
%
\begin{align}
\hphantom{\mbox{$f(x)-g(x)$}} & \hphantom{\mbox{$= x^2+x^3+x^4+x^5+b$}}\nonumber\\
g(x) &= x^2+x^3+x^4+x^5+b
\end{align}
\x\x\x

\rule{\columnwidth}{1pt}
\end{document}
