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