Question

How do you solve the system of equations `x+ y = 8` and `9x + 9y = 72`?

Answer 1

`y=-x+8`

Explanation:

if you multiple the first equation
`x+y=8`
by 9 you will get
`9x+9y=72`
which is the second equation

(therefore you actually have only one equation)

`x+y=8`
`=> y=-x+8`