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

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

1 Answer

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Answer 1 · 2016-04-21T12:48:52

$y = 6$ $y=6$
$x = - 3$ $x=-3$

Explanation:

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

subtitute equation 2 into equation 1

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

subtitute $y = 6$ $y=6$ into equation 2

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

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

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Explanation:

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