11)(x²⁴)³x⁵ (x⁶)³:x¹⁵

$$\frac{(x^{24})^3 \cdot x^5}{(x^6)^3 : x^{15}} = \frac{x^{24 \cdot 3} \cdot x^5}{x^{6 \cdot 3} : x^{15}} = \frac{x^{72} \cdot x^5}{x^{18} : x^{15}} = \frac{x^{72+5}}{x^{18-15}} = \frac{x^{77}}{x^3} = x^{77-3} = x^{74}$$

Ответ: x⁷⁴