## Elementary Algebra

$n=\{0,9\}$
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.