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

m∠1 = 120°

m∠6 = 60°

m∠6 = 60°

Because ∠1 and ∠2 are supplementary, I know that

180° - 120° = ∠2.

180° - 120° = ∠2.

Because ∠5 and ∠6 are supplementary, I know that

180° - 60° = ∠5.

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