Check #4, explain. i need answers.

Monica build a remote control toy airplane for science project to test the plane she launched it from the top of a building the plane travel a horizontal distance of 50 feet before landing on the ground a quadratic function which models the height of the plane in feet relative to the ground at a horizontal distance of x feet from the building is shown

Ineed with this problem 21 show steps

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)