How do you solve $3 x - 7 y = 28$ $3x-7y=28$ and $x + 4 y = 3$ $x+4y=3$ using substitution?

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Answer 1 · 2018-07-07T08:02:05

$x = 7, y = - 1$ $x=7,y=-1$

Adding $- 4 y$ $-4y$ to the second equation

$x = 3 - 4 y$ $x=3-4y$

plugging this in the first equation

$3 (3 - 4 y) - 7 y = 28$ $3(3-4y)-7y=28$

expanding

$9 - 12 y - 7 y = 28$ $9-12y-7y=28$

adding $- 9$ $-9$ to both sides and combining like Terms

$- 19 y = 19$ $-19y=19$

so
$y = - 1$ $y=-1$ and $x = 3 + 4 = 7$ $x=3+4=7$

How do you solve 3x-7y=283x−7y=283x-7y=28 and x+4y=3x+4y=3x+4y=3 using substitution?