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Formula
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Sum of all exterior numbers = 360°
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Apply Formula
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z + 45 + 55 + 78 + 74 + z = 360
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Combine likes term
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2z + 252 = 360
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Take away 252 from both sides
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2z = 360 - 252
2z = 108
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Divide by 2 on both sides
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2z = 108
z = 108 ÷ 2
z = 54
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Find z + 45
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z + 45 = 54 + 45
z + 45 = 99°
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Answer: 99°
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