\[14 \cdot \left( - \frac{1}{7}\sqrt{15} \right)^{2} - \frac{1}{8} \cdot \left( 2\sqrt{6} \right)^{2} =\]
\[= 14 \cdot \frac{1}{49} \cdot 15 - \frac{1}{8} \cdot 4 \cdot 6 =\]
\[= \frac{30}{7} - 3 = 4\frac{2}{7} - 3 = 1\frac{2}{7}\]