I'd start by simplifying the entire expression first...
Evaluate (a^2 * b^7) / (a^3 * b) as a fraction in index form when a = (2/5)^4 and b = (5/8)^3
Answer is 5^22/2^58, I've tried numerous ways to get to this but am struggling. When I think I'm just about there I always find a problem with my working.
Help would be greatly appreciated.