# How do you solve 3x-7y=28 and x+4y=3 using substitution?

Jul 7, 2018

$x = 7 , y = - 1$

#### Explanation:

Adding $- 4 y$ to the second equation

$x = 3 - 4 y$

plugging this in the first equation

$3 \left(3 - 4 y\right) - 7 y = 28$

expanding

$9 - 12 y - 7 y = 28$

adding $- 9$ to both sides and combining like Terms

$- 19 y = 19$

so
$y = - 1$ and $x = 3 + 4 = 7$