SOLUTION: In Triange ABC, Angle A= 120 degrees and an exterior angle at C is 5x as large a Angle B. Find measurement of Angle B.

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Question 1129710: In Triange ABC, Angle A= 120 degrees and an exterior angle at C is 5x as large a Angle B. Find measurement of Angle B.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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In Triangle ABC, Angle A= 120 degrees
and an exterior angle at C is 5x as large a Angle B.
C = 180 - 5B
A + B + C = 180
Find measurement of Angle B.
Replace C with (180-5B)
120 + B + (180-5B) = 180
B + 180 - 5B = 180 - 120
B + 180 - 5B = 60
B - 5B = 60 - 180
-4B = -120
B = -120/-4
B = +30 degrees
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Check this, find C
C = 180 - 5(30)
C = 180 - 150
C = 30 degrees also
120 + 30 + 30 = 180