\[\sqrt{\left( \sqrt{23} - 7 \right)^{2}} - \sqrt{\left( \sqrt{23} - 3 \right)^{2}} =\]
\[= \left| \sqrt{23} - 7 \right| - \left| \sqrt{23} - 3 \right| =\]
\[= 7 - \sqrt{23} - \left( \sqrt{23} - 3 \right) =\]
\[= 7 - \sqrt{23} - \sqrt{23} + 3 =\]
\[= 10 - 2\sqrt{23}\]