Answer
$9\sqrt{2xy}$
Work Step by Step
Extracting the factors that are perfect powers of the index, the given expression simplifies to
\begin{array}{l}\require{cancel}
\sqrt{50xy}+\sqrt{72xy}-\sqrt{8xy}
\\\\=
\sqrt{25\cdot2xy}+\sqrt{36\cdot 2xy}-\sqrt{4\cdot 2xy}
\\\\=
\sqrt{(5)^2\cdot2xy}+\sqrt{(6)^2\cdot 2xy}-\sqrt{(2)^2\cdot 2xy}
\\\\=
5\sqrt{2xy}+6\sqrt{2xy}-2\sqrt{2xy}
.\end{array}
By combining like radicals, the given expression simplifies to
\begin{array}{l}\require{cancel}
5\sqrt{2xy}+6\sqrt{2xy}-2\sqrt{2xy}
\\\\=
(5+6-2)\sqrt{2xy}
\\\\=
9\sqrt{2xy}
.\end{array}
