Total memberships = 40 + 50 + 60 = 150
Memberships due to people in 1 club = 70
Memberships due to people in 3 clubs = 10 * 3 = 30
150 - 70 - 30 = 50 memberships due to people in 2 clubs
50/2 = 25 different people are in 2 clubs
Probability that he has membership of exactly two clubs=25/150=1/6