Step-by-step explanation:
6. angle 1 = angle 4 = 60deg (vertically opposite angles)
7. angle 3 = 180 - 40 - 60 = 80deg (angles on a straight line are supplementary)
8. angle 5 = angle 2 = 40deg (vertically opposite angles)
9. angle 6 = angle 3 = 80deg (vertically opposite angles)
10. angle 7 = angle 5 + angle 4 = 40 + 60 = 100deg (alternate angles, //lines)
11. angle 8 = 180 - 100 = 80deg (angles on a str line are supplementary)
12. angle 9 = 180 - 80 - 40 = 60deg (angles in a triangle)
13. angle 10 = 180 - 60 = 120deg (angles on a str line are supplementary)
14. angle 11 = angle 9 = 60deg (vertically opp angles)
15. angle 12 = angle 10 = 120deg (vertically opp angles)
Topic: angles
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