How do you simplify (r(r-3)^5)/(r^3(r-3)^2)?

${\left(r - 3\right)}^{3} / {r}^{2}$
Since ${a}^{m} / {a}^{n} = {a}^{m - n}$, you can have:
$\frac{r {\left(r - 3\right)}^{5}}{{r}^{3} {\left(r - 3\right)}^{2}} = \frac{{\left(r - 3\right)}^{5 - 2}}{r} ^ \left(3 - 1\right)$
${\left(r - 3\right)}^{3} / {r}^{2}$