Answer
$x=15$
Work Step by Step
Divide $3$ to both sides:
\begin{align*}
\dfrac{3\sqrt{2x+6}}{3}&=\dfrac{18}{3}\\\\
\sqrt{2x+6}&=6\\
\end{align*}
Square both sides:
\begin{align*}
(\sqrt{2x+6}^2&=6^2\\\\
2x+6&=36
\end{align*}
Solve for $x$:
\begin{align*}
2x&=36-6\\\\
2x&=30\\\\
\frac{2x}{2}&=\frac{30}{2}\\\\
x&=15
\end{align*}
