explain please too! i really am struggling with this and I don't know how the results are achieved. thanks!

Answer:
Angle 1 = 180°-99° (adj angles on a str line)
= 81°
Angle 2 = 99° (vert opp angles)
Angle 3 = 81° (vert opp angles)
Angle 4 = 99° (corr angles, a//b)
Angle 5 = 81° (corr angles, a//b)
Angle 6 = 99° (corr angles, a//b)
Angle 7 = 81° (corr angles, a//b)