Question 237435
{{{a=p(L+rt)}}} Start with the given equation.



{{{a=pL+prt}}} Distribute



{{{a-pL=prt}}} Subtract pL from both sides.



{{{(a-pL)/(pt)=r}}} Divide both sides by pt to isolate r.



So the solution is {{{r=(a-pL)/(pt)}}}