Well count up this only shows 5 right? -2 to 3 is 5 then 3 to 8 is 5 then 8 to 13 is 5 then 13 to 18 is 5. Keep going till you get to the 9th number.
6 7 8 9
____________
23 28 33 38
38 is your final answer. Well I just hope you said 9th if not go down or up as I just told you. (by 5's)
Hoped I helped!