If three people have a 'mean' age of 36, that means the sum of all their ages is 36*3 = 108.
Since the median age is 30, we know the age of the second oldest person is 30.
Range, the difference between the ages of the oldest and youngest person, is 20.
The sum of the oldest and youngest is the sum of all three ages, 108, less the age of the middle person, so D + Y = 108 - 30 = 78
If D + Y = 78, and D-Y = 20:
20 + 2Y = 78
2Y = 58
Y = 29
Since Y is 20 less than D, the oldest person is 49
The ages are 29, 30, and 49