#### Answer

$n=\{0,9\}$

#### Work Step by Step

Squaring both sides of the inequality and using the properties of radicals, the solution to the given equation is
\begin{array}{l}\require{cancel}\left(
3\sqrt{n}
\right)^2=\left(
n
\right)^2
\\\\
9n=n^2
\\\\
0=n^2-9n
\\\\
n(n-9)=0
\\\\
n=\{0,9\}
.\end{array}
Upon checking, both solutions, $
n=\{0,9\}
,$ satisfy the original equation.