-3/64
A negative exponent you treat the same as a positive exponent, except the answer is the reciprocal (ex the reciprocal of 5 is 1/5, and the reciprocal of 3/5 is 5/3)
2^-2 is the same thing as 1/2^2, which equals 1/4. 4^0 = 1, as any number to the 0th power equals 1.
1/4-1=-3/4
4^-2 is the same thing as 1/4^2, which is 1/16.
Multiply -3/4 by 1/16, to get your answer, which is -3/64