Answer
$X=\left[\begin{array}{ll}
-2/3 & 2\\
-2/3 & 3\\
-2/3 & -4/3
\end{array}\right]$
Work Step by Step
Use the Properties of Matrix Addition (page 614)
and the Properties of Scalar Multiplication (page 616)
$3X+A=B$
... Subtract A from both sides
$3X=B-A$
... Multiply both sides with a scalar, $\displaystyle \frac{1}{3}$
$X=\displaystyle \frac{1}{3}(B-A)$
$X=\displaystyle \frac{1}{3}\left[\begin{array}{ll}
-5-(-3) & -1-(-7)\\
0-2 & 0-(-9)\\
3-5 & -4-0
\end{array}\right]=\displaystyle \frac{1}{3}\left[\begin{array}{ll}
-2 & 6\\
-2 & 9\\
-2 & -4
\end{array}\right]$
$X=\left[\begin{array}{ll}
-2/3 & 2\\
-2/3 & 3\\
-2/3 & -4/3
\end{array}\right]$
