What is 3bmatrix 2 & -1 \\ 4 & 5 bmatrix?

Scalar multiplication multiplies every entry of the matrix by the scalar: $3\cdot2=6$, $3\cdot(-1)=-3$, $3\cdot4=12$, and $3\cdot5=15$. The result is $\begin{bmatrix}6&-3\\12&15\end{bmatrix}$, choice F. Choice G adds $3$ to each entry instead of multiplying. Choice H multiplies only some entries and leaves the $-1$ and the $4$ unchanged. Choice J scales only the off-diagonal entries and leaves the $2$ and the $5$ unchanged. Every entry must be scaled, including the negative one.