\[\frac{6x - 30}{x + 8}\ :\frac{x^{2} - 25}{2x + 16} =\]
\[= \frac{6(x - 5) \cdot 2(x + 8)}{(x + 8)(x - 5)(x + 5)} =\]
\[= \frac{12}{x + 5}.\]