Question

A quadrilateral has three acute angles each measure as 80° what is the measure of 4th angle?

Answer 1

Sum of all 4 angles = 360°

80° + 80° + 80° + x° = 360°

x = 120°

Answer 2

Hello !

4 angles → 360°
Three angles → 80° × 3 = 240°
4th angle → 240° + x = 360°
x = 240° - 360° = 120°