Answer
$ \left[\begin{array}{rr}
11 & -12\\
-4 & 14
\end{array}\right]$
Work Step by Step
1. Check if the matrices have the same dimension. If they don't, the sum/difference is not defined.
2. The sum/difference will be a matrix with the same dimension.
3. Position by position, add/subtract the corresponding entries.
---
$\left[\begin{array}{ll}
11 & 0\\
-4 & 0
\end{array}\right]-\left[\begin{array}{ll}
0 & 12\\
0 & -14
\end{array}\right]=\qquad$ ... dimensions match, continue
$=\left[\begin{array}{ll}
11-0 & 0-12\\
-4-0 & 0-(-14)
\end{array}\right]$
$=\left[\begin{array}{rr}
11 & -12\\
-4 & 14
\end{array}\right]$
