\[\sqrt{32 - 10\sqrt{7}} =\]
\[= \sqrt{25 - 10\sqrt{7} + 7} =\]
\[= \sqrt{\left( 5 - \sqrt{7} \right)^{2}} = \left| 5 - \sqrt{7} \right| =\]
\[= 5 - \sqrt{7}\]