Question

How do you solve y = 1/5x +4 and x - 5y = -20?

Answer 1

Have a look:

Explanation:

Use the value of `y` from the first equation substituted into the second and solve for `x`:
`x-5(color(red)(1/5x+4))=-20`
`x-x-20=-20`
`-20=-20` true!

The two equations represent COINCIDENT lines. Basically the second is equal to the first multiplied by `5`!
The two lines lie one over the other and so have `oo` points in common and the system will then have `oo` solutions representing these points.