Answer
$\color{blue}{\dfrac{12r^3}{5}}$
Work Step by Step
Use the rule $\dfrac{a}{b} \div \dfrac{c}{d} = \dfrac{a}{b} \times \dfrac{d}{c}$ to obtain:
$\dfrac{8r^3}{6r} \times \dfrac{9r^3}{5r^2}$
Cancel common factors, then multiply to obtain:
$\require{cancel}
=\dfrac{\cancel{8}4\cancel{r^3}r^2}{\cancel{6}3\cancel{r}} \times \dfrac{9\cancel{r^3}r}{5\cancel{r^2}}
\\=\dfrac{4r^2}{3} \times \dfrac{9r}{5}
\\=\dfrac{4r^2}{\cancel{3}} \times \dfrac{\cancel{9}3r}{5}
\\=\color{blue}{\dfrac{12r^3}{5}}$
