Answer
$\left[\begin{array}{lll}
7 & 6 & 5\\
2 & -1 & 11
\end{array}\right]$
Work Step by Step
$A-D$ exists because A and D have the same order, $2\times 3.$
The product of an $m\times\underline{n}$ matrix and an $\underline{n}\times p$ matrix is an $m\times p$ matrix.
$(A-D)$ is a $2\times\underline{3}$ matrix, $C$ is $\underline{3}\times 3.$
$(A-D)C$ exists and is a $2\times 3$ matrix.
The element in the ith row and $j$th column of $(A-D)C$ is found by
multiplying each element in the $i$th row of $(A-D)$ by the corresponding element in the $j$th column of $C,$
and adding the products.
$A-D=\left[\begin{array}{lll}
2+2 & -1-3 & 2-1\\
5-3 & 3+2 & -1-4
\end{array}\right]=\left[\begin{array}{lll}
4 & -4 & 1\\
2 & 5 & -5
\end{array}\right]$
$(A-D)C=\left[\begin{array}{lll}
4 & -4 & 1\\
2 & 5 & -5
\end{array}\right]\left[\begin{array}{lll}
1 & 2 & 3\\
-1 & 1 & 2\\
-1 & 2 & 1
\end{array}\right]$
$=\left[\begin{array}{lll}
4+4-1 & 8-4+2 & 12-8+1\\
2-5+5 & 4+5-10 & 6+10-5
\end{array}\right]$
$=\left[\begin{array}{lll}
7 & 6 & 5\\
2 & -1 & 11
\end{array}\right]$
