For 1-5, you add up both angles that are stated and then subtract that number from 180 to get the missing angle. For 6, the top angle is equal to 40 since half of it equals 20. The other 2 angles are equivalent, so we subtract 40 from 180 and then divide that number by 2 to get your answer. For 7, you see two triangles on one. The first triangle has the angles of 60 and 60, and since a triangles angles add up to 180, we add both angles and subtract it from 180 to get that side. Since a straight angle is also equal to 180 degrees, the answer you just got and the answer you’re looking for are supplementary angles. So, you subtract that answer from 180 to get your answer. For 8, you do the same thing with supplementary angles. Since the straight lines is equal to 180 degrees, we subtract 144 from it to get your answer. For 9, we do the same thing that we did with number 7. The first triangles sides are 40 and 70, so we add those together and subtract it from 180 to get the missing side. That side and the one that you’re looking for are supplementary angles, so you subtract that side from 180 to get your answer.
