Answer
$z=-2$
Work Step by Step
Step 1. Subtract 7z from both sides of the equation.
$9+7z-7z=9z-7z+13$
$9=2z+13$
Step 2. Subtract 13 from both sides.
$9-13=2z+13-13$
$-4=2z$
Step 3. Divide both sides by 2.
$\frac{-4}{2}=\frac{2z}{2}$
$z=-2$
