Answer
$\left[\begin{array}{ll}
28 & 12\\
-56 & -24\\
-7 & -3
\end{array}\right]$
Work Step by Step
A product of two matrices exists
if the first has as many columns
as the second matrix has rows.
The product of an $m\times\underline{n}$ matrix $A$ and an $\underline{n}\times p$ matrix $B$
is an $m\times p$ matrix $AB$.
The product $CB$ exists because $C$ is a 2$\times\underline{2}$ matrix,
and $B$ is a $\underline{2}\times$2 matrix.
($CB$) is 2$\times$2.
The product of A ( a $3\times\underline{2}$ matrix) and $CB$ ( a $\underline{2}\times$2 matrix)
exists and is a $3\times 2$ matrix.
$CB=\left[\begin{array}{ll}
1(5)-1(-2) & 1(1)-1(-2)\\
-1(5)+1(-2) & -1(1)+1(-2)
\end{array}\right] =\left[\begin{array}{ll}
7 & 3\\
-7 & -3
\end{array}\right]$
$A(CB)=\left[\begin{array}{ll}
4 & 0\\
-3 & 5\\
0 & 1
\end{array}\right]\left[\begin{array}{ll}
7 & 3\\
-7 & -3
\end{array}\right]$
$=\left[\begin{array}{ll}
28+0 & 12+0\\
-21-35 & -9-15\\
0-7 & 0-3
\end{array}\right]$
$=\left[\begin{array}{ll}
28 & 12\\
-56 & -24\\
-7 & -3
\end{array}\right]$