Answer
$-49a^{22}b^{4}$
Work Step by Step
Based on the product rule for exponents, we know that $a^{m}\times a^{n}=a^{m+n}$ (where $m$ and $n$ are positive integers and $a$ is a real number).
Therefore, $(-7a^{3}b^{3})(7a^{19}b)=-7\times7\times a^{3+19}\times b^{3+1}=-49\times a^{22}\times b^{4}=-49a^{22}b^{4}$.