$$\frac{(3^4)^{-3}}{3^{-15}} = \frac{3^{4 \cdot (-3)}}{3^{-15}} = \frac{3^{-12}}{3^{-15}} = 3^{-12 - (-15)} = 3^{-12 + 15} = 3^3 = 27$$
Ответ: 27