Step-by-step explanation:
the item angle on the left line is also 130 degrees, as these 2 equally long lines create a triangle with 2 equal sides.
the two internal angles are the complement from 130 to 180 degrees, as every straight line stands for 180 degrees.
so, 180-130 = 50 degrees.
=> both internal angles are 50 degrees.
that makes the angle at the bottom tip of the triangle the complement of both 50 degree angle to 180, because the sum of all angles in a triangle is always 180 degrees.
so, 180 - 50 - 50 = 80 degrees.
and the outside angles of that triangle tip angle are each half of the complement of these 80 degrees to 180 (resistive to the bottom horizontal line).
180 - 80 = 100
100/2 = 50
so, both outside bottom angles are again 50 degrees.
