Answer:
D
Step-by-step explanation:
[tex]\begin{pmatrix}3\cdot \:6&3\cdot \:6&3\cdot \:4\\ 3\cdot \:7&3\left(-4\right)&3\cdot \:4\\ 3\left(-6\right)&3\cdot \:9&3\left(-3\right)\end{pmatrix}+ \begin{pmatrix}9\cdot \:1&9\cdot \:5&9\left(-8\right)\\ 9\cdot \:9&9\left(-5\right)&9\left(-8\right)\\ 9\cdot \:9&9\left(-5\right)&9\cdot \:2\end{pmatrix}\\\\=\begin{pmatrix}18&18&12\\ 21&-12&12\\ -18&27&-9\end{pmatrix}+\begin{pmatrix}9&45&-72\\ 81&-45&-72\\ 81&-45&18\end{pmatrix} \\\\\\=\begin{pmatrix}27&63&-60\\ 102&-57&-60\\ 63&-18&9\end{pmatrix}[/tex]
