How do you solve $4x + 5y = 18$ and $x = 39 -7y$ using substitution?

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Answer 1 · 2016-04-21T12:48:52

$y=6$
$x=-3$

$4x+5y=18$ -----1
$x=39-7y$ -----2

subtitute equation 2 into equation 1

$4(39-7y)+5y=18$
$156-28y+5y=18$
$156-23y=18$
$-23y=-138$
$y=6$

subtitute $y=6$ into equation 2

$x=39-7(6)$
$x=-3$

How do you solve 4x + 5y = 184x + 5y = 18 and x = 39 -7yx = 39 -7y using substitution?