How to use \begin{cases}

Question

I need to do some work, I know the command \begin{cases} do this symbol "{" at the beggining of the operation, but now I need the other one, "}" that symbol, at the end of the operation. How can I do that? I want this:

And I know how to do this:

Thanks!

Answer 1

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
  \left.
  \begin{alignedat}{3}
  x +{}&& y ={}&& 7\\
  5x -{}&& 2y ={}&& -7
  \end{alignedat}
  \right\}
\]
\end{document}

Answer 2

The package systeme does wonders for linear systems.

\documentclass{article}
\usepackage{systeme}
\begin{document}
[
\sysdelim{.}{\rbrace}
\systeme{
  x+y=7,
  5x-2y=-7
}
]
\end{document}

If you want right alignment for the right-hand sides, you can use the relevant option:

\documentclass{article}
\usepackage{systeme}
\begin{document}
[
\sysdelim{.}{\rbrace}
\sysalign{r,r}
\systeme{
  x+y=7,
  5x-2y=-7
}
]
\end{document}

Answer 3

Check out How to put a brace on the right, not left, to group cases?, I think it has what you're looking for.

An alternative to the cases environment is to use an aligned environment from amsmath with \left\{ and \right\} braces:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\begin{document}
[
\left.
    \begin{aligned}
        x + y   &= 7 \
        5x - 2y &= -7
    \end{aligned}
\right}
]
\end{document}