%% 
%%  Ein Beispiel der DANTE-Edition
%% 
%% 
%%  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.
%% 
%% 
%%Run also: >>  << 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{190.324pt}
\setlength\parindent{0pt}

\usepackage{amsmath}

\begin{document}
\begin{gather}
\boxed{i_{11}=0.25}\\
\boxed{i_{21}=\frac{1}{3}i_{11}}\nonumber\\
\boxed{i_{31}=0.33i_{22}}
\end{gather}
\end{document}