\[\frac{\sqrt{7} - \sqrt{3}}{\sqrt{35} - \sqrt{15} + \sqrt{14} - \sqrt{6}} =\]
\[= \frac{\sqrt{7} - \sqrt{3}}{\sqrt{5} \bullet \left( \sqrt{7} - \sqrt{3} \right) + \sqrt{2} \bullet \left( \sqrt{7} - \sqrt{3} \right)} =\]