g(f(x)) = 5 - 4xsimplifies to g(2x - 3) = 5 - 4x. We are trying to find g(4), so we try to make 2x - 3 equal to 4. If 2x - 3 = 4, then we know that 2x = 7, or x = 3 1 / 2. Putting this into 5-4x, we can see that 5 - 4 * 3.5, or 5 - 14, or 9. Therefore, g(4) is equal to -9.