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#### 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.

**Three interior angles of a triangle add up to ****180°****.**

Any quadrilaterals (a shape with 4 sides) can be made up with two triangles.

Since the three interior angles of a triangle adds up to **180°**, all the interior angles of a quadrilateral **adds up to 360°**.

**Finding the Unknown Angle**

360° = *a* + *b* + *c *+ *d*

360° = 100º + 85º + 90º + *d*

360° = 275º + *d*

*d* = 360° − 275º

*d* = 85º