Answer
$\left[\begin{array}{rrr}
15 & 21 & -16\\
22 & 34 & -22\\
-11 & 7 & 22
\end{array}\right]$
Work Step by Step
$A+B=\left[\begin{array}{lll}
0+4 & 3+1 & -5+0\\
1+(-2) & 2+3 & 6+(-2)
\end{array}\right]$
$=\left[\begin{array}{lll}
4 & 4 & -5\\
-1 & 5 & 4
\end{array}\right]$
C is a 3 by 2 matrix. (A+B) is a 2 by 3 matrix.
C(A+B) is defined and is a 3 by 3 matrix,
the entry $[C(A+B)]_{ij}$ = (row i of C)$\times$(column j of $ A+B$)
$C(A+B)=\left[\begin{array}{ll}
4 & 1\\
6 & 2\\
-2 & 3
\end{array}\right]\left[\begin{array}{lll}
4 & 4 & -5\\
-1 & 5 & 4
\end{array}\right]$
$=\left[\begin{array}{lll}
16-1 & 16+5 & -20+4\\
24-2 & 24+10 & -30+8\\
-8-3 & -8+15 & 10+12
\end{array}\right]$
$=\left[\begin{array}{lll}
15 & 21 & -16\\
22 & 34 & -22\\
-11 & 7 & 22
\end{array}\right]$
