How do you solve the system $2x+7y=3$ and $x = 1-4y$ by substitution?

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Answer 1 · 2015-05-24T23:47:24

Try this:
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Answer 2 · 2015-05-24T23:49:19

Substitute the formula for $x$ from the second equation into the first equation as follows:

$3 = 2x+7y = 2(1-4y)+7y = 2-8y+7y = 2-y$

Add $y$ to both ends to get:

$y + 3 = 2$

Subtract #3 from both sides to get:

$y = -1$

Substitute this value for $y$ into the original second equation to find $x$ :

$x = 1 - 4y = 1 - 4(-1) = 1+4 = 5$

How do you solve the system 2x+7y=3 2x+7y=3 and x = 1-4yx = 1-4y by substitution?