#### Answer

$12\sqrt{2}$

#### Work Step by Step

By combining like radicals, the given expression, $
8\sqrt{2}-\sqrt{2}+5\sqrt{2}
,$ simplifies to
\begin{array}{l}\require{cancel}
(8-1+5)\sqrt{2}
\\\\=
12\sqrt{2}
.\end{array}
* Note that it is assumed that all variables represent positive numbers.