Answer:
87.4°
Step-by-step explanation:
(3x + 8) + (3x + 18) + (7x + 9) = 180
3x + 8 + 3x + 18 + 7x + 9 = 180
add the common numbers
13x + 35 = 180
subtract 35
13x = 145
divide 13
x = 11.2
then plug it back in to m<3
7(11.2) + 9
78.4 + 9
= 87.4°
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