Question 681861
x is one number
y is another number
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{{{x = (2/5)y}}}
x+y = 21 : rearrange as x = 21-y
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21 - y  = (2/5)y
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Multiply the entire equation by 5
{{{5(21) - 5y = 5(2/5)y}}}
105 - 5y = 2y
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Isolate the y variable
105 = 2y + 5y
105 = 7y
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Divide both sides by 7
{{{highlight_green(y = 15)}}}
x = 21-15 = {{{highlight_green(x=6)}}}
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