**We know that mean = sum/ number**

Given that, Mean of 4 numbers = 15

⇒ Sum of the 4 numbers = 4 x 15 = 60

Mean of the first 3 numbers = 9

⇒ Sum of the first 3 numbers = 3 x 9 = 27

Mean of the first 2 numbers = 4

⇒ Sum of the first 2 numbers = 2 x 4 = 8

Fourth number = sum of 4 numbers – sum of 3 numbers = 60 – 27 = 33

Third number = sum of 3 numbers – sum of 2 numbers = 27 – 8 = 19

Second number = Sum of 2 numbers – given number = 8-2 = 6

**∴ The other three numbers are 6, 19, 33.**