Step-by-step explanation:
since the 2 lives are parallel, this makes the 2 triangles (above l and the larger one above m) similar.
and that means their angles are the same.
and that means that the third angle in the small triangle above l is also y°.
and now, remember, the sum of all angles in a triangle is always 180°.
so,
180 = x + y + z = x + 20 + 60
x = 180 - 20 - 60 = 100°
so, B is correct.
