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How do you solve $x + y = 20$ $x+y=20$ , $x = 3 y$ $x=3y$ ?

1 Answer

Apr 19, 2018

$y = 5$ $y = 5$
$x = 15$ $x = 15$

Explanation:

Substitute:

$3 y + y = 20$ $3y + y = 20$

Solve:

$4 y = 20$ $4y = 20$
$y = \frac{20}{4} = 5$ $y = 20/4 = 5$

Substitute y into the equation:

$x + 5 = 20$ $x + 5 = 20$
$x = 15$ $x = 15$

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