Question

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

Answer 1

`x=-12`
`y=-10`

Explanation:

You have the value for y. This makes substitution easier.
`y = 8x + 86`. Plug that into the other equation `8x-5y = -46`
`8x - 5 (8x + 86) = -46`
Distribute terms and combine like terms.
`8x - 40x - 430 = -46`
We are left with `-32x - 430 = -46`
Solve for x by isolating it.
Add 430 to both sides
`-32x = 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(-12) - 5y = -46`
Simplify.
`-96 - 5y = -46`
Add 96 to both sides.
`-5y = 50`
Divide both sides by -5
`y = -10`

Now, check your answers. Plug -12 for x and -10 for y in the second equation.
`8(-12) + 86 = -10`
Simplify
`-96 + 86 = -10`
`-10 = -10`