So we are given the system:
[tex]2x+4y=8\\
6x+3y=-3[/tex]
Written in matrix form we get:
[tex] \left[\begin{array}{cc}2&4\\6&3\end{array}\right]
\left[\begin{array}{c}x\\y\end{array}\right] =
\left[\begin{array}{c}8\\-3\end{array}\right] [/tex]
We compute the solution like this:
[tex]
\left[\begin{array}{c}x\\y\end{array}\right] =
\left[\begin{array}{cc}2&4\\6&3\end{array}\right] ^{-1}
\left[\begin{array}{c}8\\-3\end{array}\right]
\\=
\left[\begin{array}{cc}-3&4\\6&-2\end{array}\right]
\left[\begin{array}{c}8\\-3\end{array}\right] \dfrac{1}{18}\\=
\left[\begin{array}{c}2\\-3\end{array}\right][/tex]
The solution is :
[tex]\left[\begin{array}{c}2\\-3\end{array}\right][/tex]