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

Apr 30, 2018

By arranging the equations

#### Explanation:

First equation can be arranged as:

$4 x - 7 = y$

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

$2 x - 3 \left(4 x - 7\right) = - 9$

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

$- 10 x = - 9 - 21$

$- 10 x = - 30$

$x = 3$

y can be obtained using the first equation:

$y = 4 x - 7$

$y = \left(4 \times 3\right) - 7$

$y = 12 - 7$

$y = 5$

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