\[\sqrt{27 + 10\sqrt{2}} =\]
\[= \sqrt{25 + 10\sqrt{2} + 2} =\]
\[= \sqrt{\left( 5 + \sqrt{2} \right)^{2}} = \left| 5 + \sqrt{2} \right| =\]
\[= 5 + \sqrt{2}\]