Assuming the scooter is moving horizontally on a flat surface, then by Newton's second law, the vertical forces (the normal force and the scooter's weight) cancel out:
n - w = 0
n = w
n = (120 kg) g = 1176 N
(where g = 9.8 m/s²)
Then the friction force has a magnitude of
f = µ n
where µ is the coefficient of kinetic friction, so that
f = 0.4 (1176 N) = 470.4 N ≈ 470 N