# How do you solve 8x-5y= -46 and 8x+ 86=y using substitution?

May 29, 2018

$x = - 12$
$y = - 10$

#### Explanation:

You have the value for y. This makes substitution easier.
$y = 8 x + 86$. Plug that into the other equation $8 x - 5 y = - 46$
$8 x - 5 \left(8 x + 86\right) = - 46$
Distribute terms and combine like terms.
$8 x - 40 x - 430 = - 46$
We are left with $- 32 x - 430 = - 46$
Solve for x by isolating it.
$- 32 x = 384$
Divide both sides by -32
$x = - 12$

Oops. Forgot to solve for y.
Plug the value in for x into one of the equations.
$8 \left(- 12\right) - 5 y = - 46$
Simplify.
$- 96 - 5 y = - 46$
$- 5 y = 50$
$y = - 10$
$8 \left(- 12\right) + 86 = - 10$
$- 96 + 86 = - 10$
$- 10 = - 10$