This eighth-grade geometry worksheet introduces students to the Triangle Angle Sum Theorem and has them practice finding a missing interior angle in a triangle.

Students use the Triangle Angle-Sum Theorem to solve for the variable in triangles where two or more angle measures are linear algebraic expressions.

Find the missing angle in a triangle using addition and subtraction.

Students use the Exterior Angle Theorem to solve for the variable in triangles where two or more angle measures are linear algebraic expressions.

Find the measures of missing interior and exterior angles of triangles with this geometry worksheet!