## Elementary Algebra

$12ab^{7}$
Using $a^{m}\times a^{n}=a^{m+n}$, we obtain: $(-6ab^{4})(-2b^{3})$ =$(-6\times-2)\times(a)\times(b^{4}\times b^{3})$ =$(12)\times (a)\times(b^{3+4})$ =$(12)\times(a)\times(b^{7})$ =$12ab^{7}$