Question:
If $A=\left[\begin{array}{ccc}3 & 1 & 2 \\ 1 & 2 & -3\end{array}\right]$ and $B=\left[\begin{array}{ccc}-2 & 0 & 4 \\ 5 & -3 & 2\end{array}\right]$, find $(2 A-B)$
Solution:
$2 A=2\left(\left[\begin{array}{ccc}3 & 1 & 2 \\ 1 & 2 & -3\end{array}\right]\right)$
$=\left[\begin{array}{ccc}6 & 2 & 4 \\ 2 & 4 & -6\end{array}\right]$
$(2 A-B)=\left[\begin{array}{ccc}6 & 2 & 4 \\ 2 & 4 & -6\end{array}\right]-\left[\begin{array}{ccc}-2 & 0 & 4 \\ 5 & -3 & 2\end{array}\right]$
$=\left[\begin{array}{ccc}8 & 2 & 0 \\ -3 & 7 & -8\end{array}\right]$
Conclusion: $(2 \mathrm{~A}-\mathrm{B})=\left[\begin{array}{ccc}8 & 2 & 0 \\ -3 & 7 & -8\end{array}\right]$