Answer
$r=\frac{d}{t}$
$t=\frac{d}{r}$
Work Step by Step
We solve for $r$ by dividing by $t$:
$\displaystyle \frac{d}{t}=\frac{rt}{t}$
$r=\frac{d}{t}$
We solve for $t$ by dividing by $r$:
$\displaystyle \frac{d}{r}=\frac{rt}{r}$
$t=\frac{d}{r}$