How do you solve $x+3y=1$ and $-3x-3y=-15$ using substitution?

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Answer 1 · 2016-04-23T02:18:31

$x=7$
$y=-2$

Given_

$x+3y=1$ ---------------- (1)
$-3x-3y=-15$ -------------(2)

Solve Equation (1) for $x$

$x=1-3y$
Substitute $x=1-3y$ in equation (2)

$-3(1-3y)-3y=-15$
$-3+9y-3y=-15$
$-3+6y=-15$
$6y=-15+3=-12$
$y=(-12)/6=-2$
$y=-2$

Substitute $y=-2$ in equation (1)

$x+3(-2)=1$
$x-6=1$
$x=1+6=7$
$x=7$

How do you solve x+3y=1x+3y=1 and -3x-3y=-15-3x-3y=-15 using substitution?