Answer
$\dfrac{49}{36n^2}$
Work Step by Step
Using $\left(\dfrac{a}{b}\right)^x=\dfrac{a^x}{b^x}$, then the expression, $
\left(\dfrac{7}{6n}\right)^2
$, simplifies to
\begin{array}{l}\require{cancel}
\dfrac{7^2}{(6n)^2}
\\\\=
\dfrac{49}{(6n)^2}
.\end{array}
Using $(ab)^x=a^xb^x$, then the expression, $
\dfrac{49}{(6n)^2}
$, simplifies to
\begin{array}{l}\require{cancel}
\dfrac{49}{6^2n^2}
\\\\=
\dfrac{49}{36n^2}
.\end{array}