Question 205751
complements,,,,x+y =90,,,,,,,draw  rt  angle,,,and divide  into 2  angles,  x & y
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supplements,,,x+z=180,,,,,,,,draw  a  straight  line,,,divide into 2 angles,x&z
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let z=7y,,,given
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(1) x+z=180,but z=7y,,,x+7y =180,,,,or  x=180-7y
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(2) x+y =90,,,,,,substitute  (1) into  (2)
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(180-7y) +y =90
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-6y = -90
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y=15,,,x=180=7(15) = 75,,,,,z= 7y = 105
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checking,  x+y=90,,,,,75 +15 = 90,,,,ok
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x+z = 180,,,  75 +105 = 180,,,,ok
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z= 7y,,,,,105 = 7*15,,,,,,ok