Question:
Find the inverse of the matrix $\left[\begin{array}{cc}3 & -2 \\ -7 & 5\end{array}\right]$.
Solution:
$|A|=\left|\begin{array}{cc}3 & -2 \\ -7 & 5\end{array}\right|=1 \neq 0$
$A$ is a non-singular matrix. Therefore, it is invertible.
Let $C_{i j}$ be a cofactor of $a_{i j}$ in $A$.
The cofactors of element $A$ are given by
$C_{11}=5$
$C_{12}=7$
$C_{21}=2$
$C_{22}=3$
$\therefore A^{-1}=\frac{1}{|A|}\left[\begin{array}{ll}5 & 7 \\ 2 & 3\end{array}\right]^{T}=\left[\begin{array}{ll}5 & 2 \\ 7 & 3\end{array}\right]$