What expression is equivalent to 2^-3/2^-5?

2^2, or 4

since the exponents have the same base, we can subtract the exponent of the numerator by the exponent in the denominator.

So 2^-3 - 2^-5 = 2^ (-3 - (-5)) = 2^2

The new exponent is 2 because - 3 - (-5) is equal to 2.