Ontario Curriculum Expectation:
6.E2.3 use the properties of supplementary angles, complementary angles, opposite angles, and interior and exterior angles to solve for unknown angle measures.
Supplementary angles are two angles that add up to 180°.
Here are examples of supplementary angles.
These two angles are supplementary angles because 135° + 45° = 180°.
Angles on a straight line always add up to 180º. ∠a + ∠b = 180°