How do you solve $4x-y=7$ and $2x-3y=-9$ using substitution?

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Answer 1 · 2018-04-30T07:05:29

By arranging the equations

First equation can be arranged as:

$4x-7 = y$

Put this y into the second equation (instead of y use $4x-7$ ):

$2x - 3(4x-7) = -9$

$2x - 12x + 21 = -9$

$-10x = -9-21$

$-10x = -30$

$x = 3$

y can be obtained using the first equation:

$y = 4x-7$

$y= (4times3) - 7$

$y= 12-7$

$y= 5$

Your solution $x=3$ and $y=5$

How do you solve 4x-y=74x-y=7 and 2x-3y=-92x-3y=-9 using substitution?