Ineed serious .

if you can't see the photo that well, and are using a device that can be rotated, try rotating it to see it horizontally.

A is 180 degrees, B is 180 degrees, C is definition of complementary angle, D is 180-angle 2, and E is angle 3.

By definition of supplementary angles, m<1 + m<2 = 180 (a)
and m<2 + m<3 = 180 (b)
Then, m<1 + m<2 = m<2 + m<3 by definition of supplementary angles (c)
Subtract m<2 from each side. You get m<1 = m<3 (d) or <1 =~ <3 (e)