3. ∠1+∠2=180° and ∠2+∠3=180°
4. they are supplementary
5. ∠1+∠2=180°=∠2+∠3
6. ∠1+∠2=180°=∠2+∠3
∠2 are same in both side so ∠1=180°-∠2 =∠3=180°-∠2
7.
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