\[\frac{\sqrt{14} - 7}{2 - \sqrt{14}} = \frac{\sqrt{7}\left( \sqrt{2} - \sqrt{7} \right)}{\sqrt{2}\left( \sqrt{2} - \sqrt{7} \right)} =\]
\[= \frac{\sqrt{7}}{\sqrt{2}} = \sqrt{\frac{7}{2}} = \sqrt{3,5}\]