Untitled

\documentclass{article}
\usepackage{amsmath,amssymb, amsthm, mathtools}

\begin{document}

\begin{align*}
    \begin{cases}
        4x + 7y = 7 \\
        3x + 6y = 3
    \end{cases} & \hfill & 
    \begin{cases}
        \frac{x+y}{2} - \frac{x-y}{3} = 1 \\
        \frac{5}{2} - 2 = 1 - \frac{1}{2}x
    \end{cases}
\end{align*}
\end{document}