## Elementary Algebra

{$27$}
Rearranging the equation to separate the radical and then squaring both sides of the equation, we obtain: $\sqrt {3n}-2=7$ $\sqrt {3n}=7+2$ $\sqrt {3n}=9$ $(\sqrt {3n})^{2}=9^{2}$ $3n=81$ $x=\frac{81}{3}=27$ Therefore, the solution set is {$27$}.