Find the Missing Angle: 120-Degree Geometric Construction Problem

In this question, we are asked to find the measure of the angle marked in orange.

We can see that it is adjacent to the left vertex of the rectangle, and its sides are extensions of the rectangle’s sides. This means that the angle is directly opposite the rectangle’s vertex, where a right angle is formed.

Since all angles in a rectangle measure 90∘90∘, the angle we were asked to find is also equal to 90∘90∘.