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

1 Answer
May 29, 2018

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