Question

How do you solve `x+9y=80` and `y=-64+9x` using substitution?

Answer 1

`x=8`; `y=8`

Explanation:

Since `y=-64+9x`
let's substitute it in the first equatiom so that
`x+9(-64+9x)=80`
then let's simplify
`x-576+81x=80`
`82x=656`
`x=656/82`
`x=8`
`y=-64+9*8`
`y=8`