\[\frac{3}{\sqrt{7 + \sqrt{24}} - 1} - \frac{3}{\sqrt{7 + \sqrt{24}} + 1} =\]
\[= \frac{3 \cdot 2}{6 + 2\sqrt{6}} = \frac{6}{6 + 2\sqrt{6}} =\]
\[= \frac{3}{3 + \sqrt{6}} = \frac{3 \cdot \left( 3 - \sqrt{6} \right)}{\left( 3 + \sqrt{6} \right)\left( 3 - \sqrt{6} \right)} =\]
\[= \frac{3 \cdot \left( 3 - \sqrt{6} \right)}{9 - 6} =\]
\[= \frac{3 \cdot \left( 3 - \sqrt{6} \right)}{3} = 3 - \sqrt{6}\]