Answer:
The answer is 87°
Step-by-step explanation:
A quadrilateral has an interior angle sum of 360°.
Given that three of the four angles in a quadrilateral are 89°, 80°, and 104°, we can create the following equation where x is the missing angle:
89° + 80° + 104° + x° = 360°.
All you have to do is add all the measures up and subtract from 360°.
89° + 80° + 104° + x° = 360° →
273° + x° = 360° →
x° = 87°.
Also, for any polygon, the interior angle sum is (n – 2) × 180°, where n is the number of sides.
A quadrilateral is a polygon with four sides so it's interior angle sum must be
(4 – 2) × 180° = 2 × 180° = 360°.
