## Basic College Mathematics (9th Edition)

$r=-4$
Step 1. Subtract 9 from both sides of the equation. $2.5r+9-9=-1-9$ $2.5r=-10$ Step 2. Divide both sides by 2.5. $\frac{2.5r}{2.5}=\frac{-10}{2.5}$ $r=-4$