Answer
$X=\left[\begin{array}{ll}
1/3 & 13/3\\
-4/3 & 6\\
-7/3 & -4/3
\end{array}\right]$
Work Step by Step
$ 3X+2A=B\qquad$ ... subtract 2A from both sides
$ 3X=B-2A\qquad$ ... multiply both sides with $\displaystyle \frac{1}{3}$
$ X=\displaystyle \frac{1}{3}(B-2A)$
$X=\displaystyle \frac{1}{3}\cdot(\left[\begin{array}{ll}
-5 & -1\\
0 & 0\\
3 & -4
\end{array}\right]-2\displaystyle \cdot\left[\begin{array}{ll}
-3 & -7\\
2 & -9\\
5 & 0
\end{array}\right]) $
$X=\displaystyle \frac{1}{3}\cdot\left[\begin{array}{ll}
-5-2(-3) & -1-2(-7)\\
0-2(2) & 0-2(-9)\\
3-2(5) & -4-2(0)
\end{array}\right]$
$X= \displaystyle \frac{1}{3}\cdot\left[\begin{array}{ll}
1 & 13\\
-4 & 18\\
-7 & -4
\end{array}\right]$
$X=\left[\begin{array}{ll}
1/3 & 13/3\\
-4/3 & 6\\
-7/3 & -4/3
\end{array}\right]$