%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-2-19 on page II-141 in "Display environments as mini-pages".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.0pt}

%StartShownPreambleCommands
\usepackage{amsmath,bm}
\newenvironment{rcases}
    {\left.\begin{aligned}}
    {\end{aligned}\right\rbrace}
%StopShownPreambleCommands

\begin{document}
\begin{equation*}
 \begin{rcases}
 \bm{B}' &=-c\nabla\times\bm{E}            \\
 \bm{E}' &=c\nabla\times\bm{B} - 4\pi\bm{J}\,
 \end{rcases}
 \quad \text {Maxwell's equations}
\end{equation*}
\end{document}
