Question

What is the measure of 4?

Answer 1

∠ 4 = 80°

Explanation:

∠ 5 and 100° are vertical angles and are congruent , so

∠ 5 = 100°

∠ 4 and ∠ 5 are same- side interior angles and sum to 180° , that is

∠ 4 + ∠ 5 = 180°

∠ 4 + 100° = 180° ( subtract 100° from both sides )

∠ 4 = 80°