Answer
See below.
Work Step by Step
$\begin{bmatrix}
1& -1 \\
0& -4 \\
3&2
\end{bmatrix}-3\begin{bmatrix}
4& 6 \\
1& -3\\
-1&8
\end{bmatrix}=\begin{bmatrix}
1& -1 \\
0& -4 \\
3&2
\end{bmatrix}-\begin{bmatrix}
12& 18 \\
3& -9\\
-3&24
\end{bmatrix}=\begin{bmatrix}
1-12& -1-18 \\
0-3& -4-(-9) \\
3-(-3)&2-24
\end{bmatrix}=\begin{bmatrix}
-11& -19 \\
-3& 5 \\
6&-22
\end{bmatrix}$
