Answer
$8c\sqrt[5]{a^3}$
Work Step by Step
Using the laws of exponents, the given expression, $
\dfrac{8c}{a^{-3/5}}
,$ is equivalent to
\begin{array}{l}\require{cancel}
8ca^{3/5}
.\end{array}
Using $a^{m/n}=\sqrt[n]{a^m}=(\sqrt[n]{a})^m$, the expression, $
8ca^{3/5}
,$ simplifies to
\begin{array}{l}\require{cancel}
8c\sqrt[5]{a^3}
.\end{array}