Question

How do you solve y=2x and y=12-x?

Answer 1

`(x,y)=(color(blue)(4,8))`

Explanation:

If
`color(white)("XXX")y=2x`
and
`color(white)("XXX")y=12-x`

then
`color(white)("XXX")2x=12-x`

Adding `x` to both sides
`color(white)("XXX")3x=12`

Dividing both sides by `3`
`color(white)("XXX")x=4`

Substituting `4` for `x` back in `y=2x` gives
`color(white)("XXX")y=8`