Question

13.
#15 practice 5.1
180°
90°
139°
11°

Explanation:

Step1: Use the exterior - angle theorem

The exterior - angle theorem states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two non - adjacent interior angles.
Let the exterior angle be \(x\). The two non - adjacent interior angles are \(75^{\circ}\) and \(64^{\circ}\).
So, \(x = 75^{\circ}+64^{\circ}\)

Step2: Calculate the sum

\(x=75 + 64=139^{\circ}\)

Answer:

\(139^{\circ}\)