A.2 How do they differ?

Angles

Lines r and s are parallel. Alex finds the relationship between 1 & 5 and 2 & 6.

m1 = 120°
m6 = 60°

Alex's "Above the Line" Method
Because 1 and 2 are supplementary, I know that
180° - 120° = 2.
Because 5 and 6 are supplementary, I know that
180° - 60° = 5.
1 and 5 are both 120°, 2 and 6 are both 60°.
180° − 120° = 60°
180° − 60° = 120°
1 5
2 6