Answer:
39
Step-by-step explanation:
the answer is going up by the numbers 1,2,3,4...
you start with 4 and go up by 2
you then get 6 that's when you count up 3
you get 9 and then count up 4
which is 13 count up 5
18 count up 6
24 count up 7
31 count up 8
39
