## Basic College Mathematics (10th Edition)

$a=-2$
We are given the equation $28=-9a+10$. In order to solve, we can first subtract 10 from both sides. $28-10=-9a+10-10$ $18=-9a$ Divide both sides by -9. $\frac{18}{-9}=\frac{-9a}{-9}$ $a=-2$