## Elementary Algebra

t = $\frac{A}{Pr}$ - $\frac{1}{r}$
Using the properties of equality we obtain: $A = P + Prt$ Subtract P from both sides $A - P = Prt$ Divide both sides by Pr $\frac{A}{Pr}$ - $\frac{P}{Pr}$ = $\frac{Prt}{Pr}$ $\frac{A}{Pr}$ - $\frac{1}{r}$ = t