Answer
$\dfrac{64x^{15}}{y^{18}}$
Work Step by Step
Using the laws of exponents, the given expression, $
(4x^{5}y^{-6})^3
$, is equivalent to
\begin{array}{l}
4^{3}x^{5(3)}y^{-6(3)}
\\\\=
64x^{15}y^{-18}
\\\\=
\dfrac{64x^{15}}{y^{18}}
.\end{array}