i think it would be 15. If im wrong simply tell me, I haven't done this in a year, but I did pass geometry with As. What I did was 2x+9x+15 = 180 because I think 360 degrees would be the whole shape so I just took two sides.
I then did "-15" on both sides and got 2x+9x=165. Then I added the Xs and got 11x = 165 and then I divides by 11 on both sides and I got 15 degrees.
