Question

How do you solve `x+y=20`, `x=3y`?

Answer 1

`y = 5`
`x = 15`

Explanation:

Substitute:

`3y + y = 20`

Solve:

`4y = 20`
`y = 20/4 = 5`

Substitute y into the equation:

`x + 5 = 20`
`x = 15`