Exterior Angles of Triangles: Solve for the Variable

Use this worksheet to give learners practice using the Exterior Angle Theorem, which states that the measure of an exterior angle of a triangle is equal to the sum of the two opposite interior angles. Geared toward eighth-grade geometry learners, this worksheet asks students to use the Exterior Angle Theorem to solve for the variable in triangles where two or more of the measures of the exterior angle or opposite interior angles are linear algebraic expressions. As a warm-up, have students complete the Finding Exterior Angles of Triangles worksheet.