\[\left( \frac{a - 8^{\backslash a - 8}}{a + 8} - \frac{a + 8^{\backslash a + 8}}{a - 8} \right)\ :\frac{16a}{64 - a^{2}} = 2\]
\[= \frac{a^{2} - 16a + 64 - a^{2} - 16a - 64}{a^{2} - 64} \cdot \frac{64 - a^{2}}{16a} =\]
\[= \frac{- 32a}{a^{2} - 64} \cdot \frac{- (a^{2} - 64)}{16a} = 2\]