As the sum of the angles in a triangle is 180 ° and all four angles in a rectangle are 90 °, then sum of the two marked angles in the triangle 180 ° - 90 ° = 90 °.
Each interior angle of a regular hexagon is 120 ° and the sum of the angles in a quadrilateral is 360 °; hence the sum of the two marked angles in the quadrilateral is 360 ° - 90 ° - (360 ° - 120 °) = 30 °.
Hence the sum of the four marked angles is 90 ° + 30 ° = 120 °.