# How do you solve the system of equations x= - 4 and - 8x - 5y = - 18 by using substitution?

Mar 14, 2017

Y is equal to 10. For how, see the explanation.

#### Explanation:

Substitute $x$ with $- 4$ in the second equation.
This gets you:
$- 8 \left(- 4\right) - 5 y = - 18$
Multiply $- 8$ and $- 4$:
$32 - 5 y = - 18$
Subtract 32 from both sides:
$- 5 y = - 50$
Divide both sides by negative five:
$y = 10$
You don't need to find x, since it's already given.
There are other ways to solve this with substitution, involving adding or subtracting different things in a different order, but they all end up with the same answer.