How do solve the following linear system?: $3x + y =20 , -3x -8y = -9$ ?

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How do solve the following linear system?: $3x + y =20 , -3x -8y = -9$ ?

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Answer 1 · 2016-03-09T23:29:24

$x=(151/21)$ and $y=(-11/7)$ or in other words the solution is the ordered pair $(151/21,-11/7)$

Explanation:

We will use the "Elimination Method" to help us start to solve this problem. I can easily eliminate the $x$ variable by addind the two equations:
$3x+y =20$
$-3x-8y=-9$ by adding like terms we get:

$-7y =11$
$y =-11/7$
Now that I have a value for $y$ , I will substitute that in the first equation and solve for $x$
$3x+y=20$
$3x +(-11/7) = 20$
$3x = 20+11/7$ I need a common denominator, which is $7$
$3x = 140/7 + 11/7$
$3x=151/7$ Divide both sides of the equation by $3$
$x=151/21$

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How do solve the following linear system?: $3x + y =20 , -3x -8y = -9$ ?

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How do solve the following linear system?: 3x + y =20 , -3x -8y = -9 3x + y =20 , -3x -8y = -9 ?

1 Answer

Explanation:

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How do solve the following linear system?: $3x + y =20 , -3x -8y = -9$ ?