Answer:
(A) 3(x +5) +(5x +15) +7x = 180
(B) x = 10
(C) A = 45°, B = 65°, C = 70°
Explanation:
A)
The sum of angles in a triangle is 180°.
m∠A +m∠B +m∠C = 180°
3(x +5) +(5x +15) +7x = 180 . . . . . substitute given expressions
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B)
15x +30 = 180 . . . . . . . . . . . . . simplify
15x = 150 . . . . . . . . . . . . . . subtract 30
x = 10 . . . . . . . . . . . . . . divide by 15
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C)
The angle measures are found from the given expressions:
m∠A = 3(x +5) = 3(10 +5) = 45
m∠B = 5x +15 = 5(10) +15 = 65
m∠C = 7x = 7(10) = 70
m∠A = 45°, m∠B = 65°, m∠C = 70°