#### Answer

$-\frac{8b}{13a^{2}}$

#### Work Step by Step

We use the rule $\frac{a^{m}}{a^{n}}=a^{m-n}$ to help us cancel out common factors in the numerator and denominator:
$\frac{-24a^{3}b^{3}}{39a^{5}b^{2}}$
=$\frac{-24}{39}\times\frac{a^{3}}{a^{5}}\times\frac{b^{3}}{b^{2}}$
=$\frac{-8}{13}\times a^{3-5}\times b^{3-2}$
=$-\frac{8}{13}\times a^{-2}\times b^{1}$
=$-\frac{8}{13}\times \frac{1}{a^{2}}\times b^{1}$
=$-\frac{8b}{13a^{2}}$