Answer
$\dfrac{1}{\sqrt[3]{y^5}}$
Work Step by Step
RECALL:
(i) $\sqrt[n]{a^m} = a^{\frac{m}{n}}$
(ii) $a^{-m} = \dfrac{1}{a^m}, a\ne0$
Use rule (ii) above to obtain:
$=\dfrac{1}{y^{\frac{5}{3}}}$
Use rule (i) above, where m=5 and n=3, to obtain:
$=\dfrac{1}{\sqrt[3]{y^5}}$