Выполните действия: (3x-15)/(x+4):(x^2-25)/(3x+12).

\[\frac{3x - 15}{x + 4}\ :\frac{x^{2} - 25}{3x + 12} =\]

\[= \frac{3x - 15}{x + 4} \cdot \frac{3x + 12}{x^{2} - 25} =\]

\[= \frac{3(x - 5) \cdot 3(x + 4)}{(x + 4)(x - 5)(x + 5)} = \frac{9}{x + 5}.\]