Answer
$\left[\begin{array}{rrr}
-12 & -3 & 0\\
6 & -9 & 6
\end{array}\right]$
Work Step by Step
If $k$ is a real number and $A$ is an $m$ by $n$ matrix,
the matrix $kA$ is the $m$ by $n$ matrix formed by multiplying each entry $a_{ij}$ in $A$ by $k$.
$-3B=-3\cdot\left[\begin{array}{lll}
-3\cdot 4 & -3\cdot 1 & -3\cdot 0\\
-3\cdot(-2) & -3\cdot 3 & -3\cdot(-2)
\end{array}\right]$
$=\left[\begin{array}{rrr}
-12 & -3 & 0\\
6 & -9 & 6
\end{array}\right]$
