Step-by-step explanation:
which angle ? all of them ?
in such a case of intersection the various angles are mirrored or have to fulfill the complementary 180 degree criteria.
when we look either on the top or the bottom of the intersected line, there is always a half circle that can be drawn with its center in the intersection point.
therefore, the sum of such 2 neighboring angles (like 1 and 43 degrees) must be 180 degrees. the same for 2 and 3.
at the same time 2 is a mirrored version of 43 degrees, and 3 is a mirrored version of 1.
so,
1 + 43 = 180
1 = 137 degrees
2 = 43 degrees
3 = 137 degrees
