#### Answer

$x=\{ -18,6 \}$

#### Work Step by Step

Taking the square root of both sides (the Square Root Property), the solutions to the given equation, $
(x+6)^2=144
,$ are
\begin{array}{l}\require{cancel}
(x+6)=\pm\sqrt{144}
\\\\
x+6=\pm\sqrt{(12)^2}
\\\\
x+6=\pm12
\\\\
x=-6\pm12
.\end{array}
Hence, $
x=\{ -18,6 \}
.$