答案1
我建议你嵌入一个
\left\{ \begin{aligned} ... \end{aligned} \right.
在普通equation
环境中进行构建。
\documentclass{article} % or some other suitable document class
\usepackage{amsmath} % for 'aligned' environment
\begin{document}
\begin{equation}
\left\{
\begin{aligned}
a &= b+c \\
d &= e+f \\
g &= h+i \\
j &= k+l
\end{aligned}
\right.
\end{equation}
\end{document}