Answer
$\left[\begin{array}{ll}
-\sqrt{3} & -13\\
4 & -2\sqrt{5}\\
-1 & -\sqrt{2}
\end{array}\right]$
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.
---
$\left[\begin{array}{ll}
\sqrt{3} & -4\\
2 & -\sqrt{5}\\
-8 & \sqrt{8}
\end{array}\right]-\left[\begin{array}{ll}
2\sqrt{3} & 9\\
-2 & \sqrt{5}\\
-7 & 3\sqrt{2}
\end{array}\right]=$
... dimensions match, continue
$=\left[\begin{array}{ll}
\sqrt{3}-2\sqrt{3} & -4-9\\
2-(-2) & -\sqrt{5}-\sqrt{5}\\
-8-(-7) & \sqrt{8}-3\sqrt{2}
\end{array}\right]$
$=\left[\begin{array}{ll}
-\sqrt{3} & -13\\
4 & -2\sqrt{5}\\
-1 & 2\sqrt{2}-3\sqrt{2}
\end{array}\right]$
$=\left[\begin{array}{ll}
-\sqrt{3} & -13\\
4 & -2\sqrt{5}\\
-1 & -\sqrt{2}
\end{array}\right]$
