Rehan is 30 years older than his son and 3 years older than his wife. The son's age will be double what it is today 9 years from now. What is their average age today?

If the son's age doubles in 9 years then s + 9 = 2s, so the son is 9 today. Rehan is 9 + 30 = 39 and his wife is 39 - 3 = 36. The three ages add to 39 + 36 + 9 = 84, so the average is 84/3 = 28 years. 37 takes the son to be 18 - his age 9 years from now rather than today - which gives 48, 45 and 18 and an average of 37. 84 is the total of the three ages, not their average. 39 is Rehan's own age.