Question 466664
"Angle DEF and Angle ABC are supplementary angles and Angle DEF if four times as large as angle ABC. Determine the measure of each angle."


x = DEF
180 - x = ABC {supplementary angles add up to 180°}


x = 4(180 - x) {DEF is four times ABC}
x = 720 - 4x {used distributive property}
5x = 720 {added 4x to both sides}
x = 144 {divided both sides by 5}
180 - x = 36 {substituted 144, in for x, into 180 - x}


DEF = 144° and ABC = 36°
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