Simplify:

((4/x)^(n-m))×((2x^2)^m)

I don't even know where to start

use your rules for powers

recall:
x^a × x^b = x^(a+b)
(x^a)^b = x^(ab)
x^-a = (1/x^a)

((4/x)^(n-m))×((2x^2)^m)
= ((2^2 x^-1)^(n-m))×((2x^2)^m)
= 2^(2n-2m) x^(m-n) × (2^m x^2m)
= 2^(2n-m) x^(3m-n)

check my arithmetic