## Elementary Algebra

Substitute 652 for A, 400 for P, and 0.07 for r to obtain : 652 = 400 + 400 $\times$ 0.07 $\times$ t 652 = 400 + 28 $\times$ t Subtract 400 from both sides. 652 - 400 = 400 - 400 + 28 $\times$ t 252 = 28 $\times$ t Divide both sides by 28 $\frac{252}{28}$ = t t = 9