Threeangles of a quadrilateral are equal and its fourth angel is 120°. Find all the angels

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.