<7 = 30
<7 = <5 vertical angles
<5 = <3 alternate interior angles
<3 + <2 = 180 straight line
30 + <2 = 180
<2 = 180 -30
<2 = 150
<10 = <12 vertical angles
<11 + <12 = 180
<11 + 80 = 180
<11 = 100
<7+<13+<12 = 180 it forms a triangle
30 + <13 + 80 = 180
110 +< 13 = 180
< 13 = 180-110
< 13 = 70
<13 = <15 vertical angles
< 15 = <17 alternate interior angles
< 17 = <19 vertical angles
< 19 = 70