Exercise 1 Page 260

According to the Exterior Angle Theorem, the measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles. Let's write an equation applying this theorem. 30^(∘)+80^(∘)=x^(∘) ⇒ x=110^(∘) We found that x=110. Therefore, the measure of the exterior angle is 110^(∘).