Answer
$-3$ must be multiplied to both sides if the equation, not $3$.
The correct solution is $m=12$.
Refer to the correct work in the step-by-step part below.
Work Step by Step
To solve the equation $-3$ must be multiplied to both sides of the equation, not $3$.
Thus, the correct solution is:
$\begin{align*}
-\frac{m}{3}&=-4\\
-3 \cdot \left(-\frac{m}{3}\right)&=-4(-3)\\
m&=12
\end{align*}$
