last number is 9 as it is series 2, 3, 4, 5, 6, 7, 8, 9 first number is 8 as it is series 1, 2, 3, 4, 5, 6, 7, 8
Middle number is 90 series is 6, 12, 20, 30, 42, 56, 72, 90 (72+18)
So number is 8909