How do you solve $7x+2y= -29$ and $-8x+y=43$ using substitution?

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Answer 1 · 2017-04-18T06:21:33

$x=-5$
$y=3$

Given -

$7x+2y=-29$ -----------------(1)
$-8x+y=43$ ------------------(2)

Solve the 2nd equation for $y$

$y=43+8x$

Substitute $y=43+8x$ in equation (1)

$7x+2(43+8x)=-29$
$7x+86+16x=-29$
$23x=-29-86 =-115$
$x=(-115)/23=-5$
$x=-5$

Substitute $x=-5$ in equation (2)

$-8(-5)+y=43$
$40+y=43$
$y=43-40=3$
$y=3$

How do you solve 7x+2y= -297x+2y= -29 and -8x+y=43-8x+y=43 using substitution?