To solve this problem, you have to know all the identities and rules to figure out that:
∠1 = ∠7 = ∠3 = ∠5 = ∠9 = ∠11
and
∠2 = ∠4 = ∠8 = ∠6 = ∠9 = ∠12
10. ∠3 + ∠2 = 180
72 + ∠3 = 180
m∠3 = 108°
11. ∠4 = ∠12
m∠12 = 84°
12. ∠1 = ∠3 = ∠5
m∠5 = 127°
13. ∠9 + ∠12 = 180
132 + ∠12 = 180
m∠12 = 48°
14. ∠6 + ∠12 = 180
69 + ∠12 = 180
m∠12 = 111°
15. ∠1 = ∠9 = ∠11
m∠11 = 110°
16. ∠4 = ∠12 = ∠10
∠9 + ∠10 = 180
∠9 + 72 = 180
m∠9 = 108°
