The third angle of the triangle must be 70 because the angles of a triangle must add up to 180. If the 80 degree angle is bisected so that the bisector meets the opposite side of the triangle splitting it into two triangles, then the angles on either side of the angle bisector will be 70 and 110, making one of the triangle isosceles (40, 70, 70) while the other triangle has angles 40, 30 and 110. Since no side lengths are given it appears that x, y and z are angles of the newly formed triangles.