# How do you solve 4x+3y=-5 and x-y=-3 using substitution?

Jul 11, 2016

$x = - 2 \mathmr{and} y = 1$

#### Explanation:

In this answer, I have subbed in for x. A solution that subbed in for y would be equally valid (and might be instructive for you to do to check you get the same answer!).

Rearrange the second equation to obtain:

$x = y - 3$

Sub this into the first expression:

$4 \left(y - 3\right) + 3 y = - 5$

$4 y - 12 + 3 y = - 5$

$7 y = 7 \implies y = 1$

$x = y - 3 = 1 - 3 = - 2$