That one is quite simple. On the sketch, you get

w+x+y+z=360º

Making the substitution with x+y=w+z, you get

w+w+z+z=360º <=> 2(w+z)=360º <=> w+z=180º

Proving AOB is a line, because the sketch provides, that w+z is an angle of AOB.

I am pretty sure, you were not asking for the proof, but I wanted to do it anyways. Does a genuine proof count as an anti meme?