Answer
$-3C=\begin{bmatrix}
-3 & -6
\\
9 & -3
\end{bmatrix}$
Work Step by Step
Multiplying each element of $
C=
\begin{bmatrix}
1 & 2
\\
-3 & 1
\end{bmatrix}
$ by $-3,$ then
\begin{align*}
-3C&=
\begin{bmatrix}
1(-3) & 2(-3)
\\
-3(-3) & 1(-3)
\end{bmatrix}
\\\\&=
\begin{bmatrix}
-3 & -6
\\
9 & -3
\end{bmatrix}
.\end{align*}
Hence, $
-3C=\begin{bmatrix}
-3 & -6
\\
9 & -3
\end{bmatrix}
.$