Three angles of a quadrilateral are equal and the measure of the fourth angle is 120°.
Question:

Three angles of a quadrilateral are equal and the measure of the fourth angle is 120°. Find the measure of each of the equal angles.

Solution:

Three angles of a quadrilateral are equal and the measure of the fourth angle is 120°.

Find the measure of each of the equal angles.

$\therefore x+x+x+120=360$

$3 x+120=360$

$3 x=240$

$x=\frac{240}{3}=80$

Each of the equal angles measure 80°.