Not really understanding the question, more info?
THEOREM:
- Angle sum property —: The sum of interior angles of a triangle is 180°.
ANSWER:
Let the missing angle be x.
By angle sum property,
- ∠x + 20° + 80° = 180°
- ∠x + 100 = 180°
- ∠x = 180° – 100°
- ∠x = 80°
So, <u>Correct choice</u> - [C] 80°.
