2. In a right triangle the acute angles are complementary, adding to 90°
Answer: 50°
3. In a triangle the angles add to 180°
Answer: 30°
4. Two lines crossing make angles that are linear pairs, supplementary, adding to 180°. So the interior angle next to 155° is 25°. So the two angles so far add to 25° + 60° = 85°.
The remaining triangle angle is the supplement of that (all three add to 180) and the exterior ? angle forms a linear pair with that one, so is the supplement of the supplement, which is the angle itself.
Answer: 85°
5. The interior supplement to 156° is 24°. The missing angle in the bottom triangle is 180°-20°-35° = 125°. Those are vertical angles so 125° is also the angle in the second triangle.
The triangle angles sum to 180° so the ? angle is
? = 180° - 24° - 125° = 31°
Answer: 31°
6. We have 55° left in the left triangle, and 180°-55°-50°=75° for the left angle in the right triangle. That leaves ?=180°-75°-35°=70°
Answer: 70°
