9514 1404 393
Answer:
r = 120t/(120 -t)
Step-by-step explanation:
Given t = f(r), solve for r.
[tex]t(r+120)=120r \qquad\text{multiply by $r+120$}\\\\rt+120t=120r \qquad\text{eliminate parentheses}\\\\rt-120r=-120t \qquad\text{subtract $120t+120r$}\\\\r(t-120)=-120t \qquad\text{factor}\\\\r=\dfrac{-120t}{t-120} \qquad\text{divide by $t-120$}\\\\\boxed{r=\dfrac{120t}{120-t}} \qquad\text{negate numerator and denominator}[/tex]
