Think about it, try to plug it in with 2 first.
40 x 2 = 80
80 + 15 is 95, and 15 x 2 = 30, the total being 125. This is incorrect, because the two angles should add up to 180 degrees. So 2 is incorrect.
Now, try 3.
40 x 3 = 120
120 + 15 = 135
15 x 3 = 45
135 + 45 = 180.
So your last option, 3, is correct. I hope this was helpful!!
