%% 
%%  Example 02-18-1 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{gather*}
  \begin{align*}
    m_2 &=  m_2' + m_2''\\
        &= \frac{V_2'}{v_2'} + \frac{V_2''}{v_2''}
  \end{align*}\\
  \Rightarrow m_2 v_2' = V - V_2'' + V_2''\frac{v_2'}{v_2''}\\
\end{gather*}
\begin{gather*}
  \begin{align*}
    m_2 &=  m_2' + m_2''\\
        &= \frac{V_2'}{v_2'} + \frac{V_2''}{v_2''} & %<<<====
  \end{align*}\\
  \Rightarrow m_2 v_2' = V - V_2'' + V_2''\frac{v_2'}{v_2''}\\
\end{gather*}
\end{document}
