Answer:
B
Step-by-step explanation:
Express the equation using positive exponent.
(a/b)^-n → (b/a)^n
The equation then becomes: (4^5/b^7)^3
Then, simplify the power 3 by multiplying the power 5 to 3 and 7 to 3
You get: 4^15/b^21
Therefore your answer being 4^15/b^21
