Answer
$\dfrac{y^{6}}{64}$
Work Step by Step
We distribute the 3 into the parenthesis in order to simplify. Furthermore, using the laws of exponents, the given expression, $
\left( \dfrac{y^2}{4} \right)^{3}
,$ simplifies to
\begin{array}{l}\require{cancel}
\dfrac{y^{2(3)}}{4^3}
\\\\=
\dfrac{y^{6}}{64}
.\end{array}
