# How do you solve 4x+5y=12 and -9+y=71 using substitution?

May 13, 2018

$x = - 97 \mathmr{and} y = 80$

#### Explanation:

Substitution will be a good method in this case because there is a single $y$ in the second equation.

$y = 71 + 9 = 80$

$4 x + 5 y = 12$

$4 x + 5 \left(80\right) = 12$

$4 x = 12 - 400$

$4 x = - 388$

$x = - 97$

Check for $x = - 97 \mathmr{and} y = 80$

$4 \left(- 97\right) + 5 \left(80\right) = 12$