**\newenvironment{ncases}[4]{%**

**\parbox{0.5\textwidth}{%**

**\begin{equation*}**

**#1=**

**\begin{cases}**

**#2**

**\end{cases}**

**\end{equation*}}**

**\hfill**

**\parbox{1cm}{%**

**\begin{eqnarray}**

**{}\label{#3}\\**

**{}\label{#4}**

**\end{eqnarray}}}**

Note: this command only supports two equations, if needed one can extend it easily to the number you want.

2) Use that command instead of the case command:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

**\newenvironment{ncases}[4]{%**

**\parbox{0.5\textwidth}{%**

**\begin{equation*}**

**#1=**

**\begin{cases}**

**#2**

**\end{cases}**

**\end{equation*}}**

**\hfill**

**\parbox{1cm}{%**

**\begin{eqnarray}**

**{}\label{#3}\\**

**{}\label{#4}**

**\end{eqnarray}}}**

\begin{document}

\begin{spacing}{1.1}

**\begin{ncases}**

**{|x|}{x, &\text{if $x\ge 0$}\\**

**-x,&\text{if $x\le 0$}}{pos}{neg}**

**\end{ncases}**

**For if $x\ge 0$, then by Equation~\eqref{pos}, we have $|x|=x\ge0$ and **

**if $x\le0$, then by Equation~\eqref{neg}, we have $|x|=-x\ge0$. **

\end{spacing}

\end{document}