Answer
$24x^{19}$
Work Step by Step
Using $(ab)^x=a^xb^x$, then the expression, $
(2x^5)^3(3x^4)
$, simplifies to
\begin{array}{l}\require{cancel}
(2^3x^{5(3)})(3x^4)
\\\\=
(8x^{15})(3x^4)
.\end{array}
Using $a^x\cdot a^y=a^{x+y}$, then given expression, $
(8x^{15})(3x^4)
$, simplifies to
\begin{array}{l}\require{cancel}
8\cdot3x^{15+4}
\\\\=
24x^{19}
.\end{array}