Question

Type the next number in this sequence:

9, 11, 15, 21, 29, 39,

Answer 1

51. You add 2, then 4, then 6, then 8, etc

Answer 2

I think that this is a pattern where it adds up to this +2 , +4 , +6 , + 8 , + 10.
So for the next number you should add 12 to 39.

12 + 39 = 51

Answer = 51