$$\frac{(a^2)^3b^4}{ab^8} = \frac{a^6b^4}{ab^8} = \frac{a^5}{b^4}$$
При a = 5, b = 4:
$$\frac{a^5}{b^4} = \frac{5^5}{4^4} = \frac{3125}{256} = 12 \frac{53}{256}$$
Ответ: 12,21