Equation practice with angle addition

Question

I need to know how to solve this 

Answer 1

Angle addition problems come from specific geometric diagrams (figures).

you may have the measures of two adjacent angles adding up to 180 degrees (supplementary angles) or 90 degrees (complementary angles). The sum of all three interior angles of any triangle is always 180 degrees in plane geometry.

The measure of one exterior angles of a triangle equals the sum of the two remote interior angles.

These are some of the typical geometry situations leading to equations, which you can solve.