Question

Three angles of a quadrilateral are equal and the measure of the fourth angle is ${120}^{\circ }$. Find the measure of each of the equal angles.

Answer 1

Let the three angles measure $x^{\circ }$ each. And
The fourth angle be $={120}^{\circ }$
Sum of all the angles of a quadrilateral is ${360}^{\circ }$.
$\Rightarrow x+x+x+120=360$
$\Rightarrow 3x+120=360$
$\Rightarrow 3x=360-120$
$\Rightarrow 3x=240$
$\therefore x=\frac{240}{3}=80$
Each of the equal angles measure ${80}^{\circ }$.