Answer
$t=\dfrac{A-P}{Pr}$
Work Step by Step
Using the properties of equality, in terms of $t,$ the given equation, $
A=P+Prt
,$ is equivalent to
\begin{array}{l}\require{cancel}
A-P=Prt
\\\\
\dfrac{A-P}{Pr}=t
\\\\
t=\dfrac{A-P}{Pr}
.\end{array}