How do you solve $2x+9y=17$ , $x=7-4y$ ?

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Answer 1 · 2017-02-25T12:44:31

x= -5
y= 3

Generally, you can solve linear systems in different ways:

1) Graphing

2) Substitution

3) Elimination.

In this case, since x is already isolated in the second equation, we would use substitution.

$2x + 9y = 17$ Then we substitute $x = 7-4y$

$2(7-4y) + 9y = 17$

$14-8y + 9y = 17$

$y=3$

Then solve for x using either equation (I picked the second one)

$x = 7 - 4y$
$x = 7 - 4(3)$
$x = -5$

How do you solve 2x+9y=172x+9y=17, x=7-4yx=7-4y?