Answer
$18a^{3}b^{6}$
Work Step by Step
We are given the expression $(-6a^{2}b^{3})(-3ab^{3})$. We can group like terms to simplify.
$(-6\times-3)\times(a^{2}\times a)\times (b^{3}\times b^{3})$
To simplify the second and third terms, we can use the product rule, which holds that $a^{m}\times a^{n}=a^{m+n}$ (where a is a real number, and m and n are positive integers).
$18\times a^{2+1} \times b^{3+3}=18a^{3}b^{6}$