#15- The answer should be 35.
In the photo I included, both points A and B are equal, because they are intersecting. To get the measurement for these angles, you add 40+40 to get 80. We know that three angles in a triangle need to add up to 180, so you would subtract 80 to get 100. If point A and B are 100, that means you can add 100+45 to get 145, and subtract that from 180 to get your answer. (35)
#16- The answer should be 42. Using the same logic as before, take away 80+40 from 180 to get 60 for points A and B. Then you would subtract 78+60 from 180 to get your answer. (42)
#17- The answer should be 108. You need to find the final angle of the triangle by subtracting 37+71 from 180. This would equal 72. Since the angle of a line is 180 degrees, you would subtract 72 from 180 to get the finished product. (108)
#18- The answer should be 35. You would start by finding the bottom left angle. You would use the same logic as I did in #17 by subtracting 180-126. This tells you that the bottom left angle in the triangle is 54. Then you would subtract 91+54 from 180 to get your answer. (35)
I hope this helps and that it wasn’t too confusing. #17 and #18 aren’t my strong suit, so I’m sorry if I’m wrong. Please mark brainliest!