Answer
$x-6\sqrt{x+5}+14$
Work Step by Step
Using $(a+b)^2=a^2+2ab+b^2$, or the square of a binomial, and the properties of radicals, the given expression, $
(3-\sqrt{x+5})^2
,$ is equivalent to
\begin{array}{l}\require{cancel}
(3)^2+2(3)(-\sqrt{x+5})+(-\sqrt{x+5})^2
\\\\=
9-6\sqrt{x+5}+x+5
\\\\=
x-6\sqrt{x+5}+(5+9)
\\\\=
x-6\sqrt{x+5}+14
.\end{array}