Answer:
Each of the three congruent angles has measure 80 deg. The fourth angle has measure 120 deg.
Step-by-step explanation:
The sum of the measures of the angles of an n-sided polygon is (n - 2)180.
A quadrilateral has 4 sides, so n = 4 in the formula above.
(n - 2)180 = (4 - 2)180 = 2(180) = 360
The sum of the measures of the angles of a quadrilateral is 360 degrees.
Three angles are congruent. Let the measures of the three congruent angles be x. The sum of the measures of the 3 angles is x + x + x = 3x.
The sum of the measures of the angles is 360 deg.
3x + 120 = 360
Subtract 120 from both sides.
3x = 240
Divide both sides by 3.
x = 80
Answer: Each of the three congruent angles has measure 80 deg. The fourth angle has measure 120 deg.
