Interior Angles in Triangles: Solve for the Variable

Use this worksheet to help students explore the Triangle Angle-Sum Theorem, which states that the measures of the interior angles of a triangle add up to 180°. In this eighth-grade geometry worksheet, students will use the Triangle Angle-Sum Theorem to solve for the variable in triangles where two or more angle measures are linear algebraic expressions. As a warm-up, have students complete the Finding Missing Angles in Triangles worksheet.