Let's label the angles where the measure is given and focus on the upper triangle.
Notice that we are given the measure of an exterior angle and a remote interior angle of a triangle. We are asked to find the measure of the other remote interior angle.
The Exterior Angle Theorem states that the measure of an exterior angle is the sum of the measures of the two remote interior angles. We can use this to set up and solve an equation for m∠ 1.
