Answer
$\left[\begin{array}{lll}
2 & 3 & 8\\
21 & 5 & 5
\end{array}\right]$
Work Step by Step
If $A$ is a matrix and $c$ is a scalar, then $cA$ is the matrix formed by multiplying each element in $A$ by $c$.
$3A=\left[\begin{array}{lll}
6 & -3 & 6\\
15 & 9 & -3
\end{array}\right],\quad 2D=\left[\begin{array}{lll}
-4 & 6 & 2\\
6 & -4 & 8
\end{array}\right]$
To add two matrices, they must have the same order.
The resulting matrix has elements obtained by adding the corresponding elements of the two matrices.
$3A$ and $2D$ are both $2\times 3$ matrices, so their sum exists.
$3A+2D=\left[\begin{array}{lll}
6-4 & -3+6 & 6+2\\
15+6 & 9-4 & -3+8
\end{array}\right]$
$=\left[\begin{array}{lll}
2 & 3 & 8\\
21 & 5 & 5
\end{array}\right]$
