\documentclass[10pt]{report}
\usepackage{a4wide}
\usepackage{epsfig}
\usepackage{array}
\usepackage{amsmath}
\usepackage{stmaryrd}
\usepackage{SIunits}
\usepackage{graphics}
\usepackage{psfrag}
\usepackage{relsize}
\usepackage[section]{placeins}
\usepackage{listings}

\begin{document}

\begin{align}
A &= 
\begin{cases}
\begin{array}{ll}
B & \mathrm{C}\\
D & \text{E}
\end{array}
\end{cases}\\
F &= 
\begin{cases}
\begin{array}{ll}
G & H\\
I & J
\end{array}
\end{cases}
\end{align}

\end{document}
