\[\frac{x^{2} - 49}{3x - 24}\ \ :\frac{5x + 35}{x - 8} =\]
\[= \frac{(x - 7)(x + 7)}{3 \cdot (x - 8)}\ :\frac{5 \cdot (x + 7)}{x - 8} =\]
\[= \frac{(x - 7)(x + 7)(x - 8)}{3 \cdot (x - 8) \cdot 5 \cdot (x + 7)} = \frac{x - 7}{15}\]