butuh bantuan kaak...........

f (2x - 1) = 4x + 5

Dit : f (3) .. ?

2x - 1 = 3
2x = 3 + 1
x = 4 / 2
x = 2

f(3) = 4 (2) + 5
f(3) = 8 + 5
f(3) = 13