Every number (except the first one) Is 5, 10, 15, 20,.... more than the previous number. 10 + 5 + 15                40 + 20 =  15 + 10 = 25              60 + 25 = 85 25 + 15 = 40              85 + 30 = 115 115 + 35 = 150 $\therefore$The missing number Is 60.