Answer
$\dfrac{x^{35}}{y^{14}}$
Work Step by Step
Using $\left(\dfrac{a}{b}\right)^x=\dfrac{a^x}{b^x}$, then the expression, $
\left(\dfrac{x^5}{y^2}\right)^7
$, simplifies to
\begin{array}{l}\require{cancel}
\dfrac{(x^5)^7}{(y^2)^7}
.\end{array}
Using $(a^x)^y=a^{xy}$, then the given expression, $
\dfrac{(x^5)^7}{(y^2)^7}
$, simplifies to
\begin{array}{l}\require{cancel}
\dfrac{x^{5(7)}}{y^{2(7)}}
\\\\=
\dfrac{x^{35}}{y^{14}}
.\end{array}
