f(x) = (1/4) x + 3 write f(x) as y
y = (1/4)x + 3 the object is to get x by itself and then "exchange" x and y
Subtract 3 from both sides
y - 3 = (1/4)x multiply both sides by 4
4y - 12 = x "exchange" x and y
4x - 12 = y
For y, write f-1 (x)
4x - 12 = f-1(x) = 4(x - 3) = "C"
