Question 1081238
D is not one of your angles.
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Proof:
2y + 3 + 9y − 7 + 7y + 4 = 180 (the three angles of EVERY triangle sum 180)
Group like terms
2y+9y+7y+3-7+4 =180
18y = 180
y = 10
Substitute y with 10 in the equations above to get your answers:
2(10)+3 = 
9(10)-7 = 
7(10)+4 =