Question

How do you solve `x+3y=7`, `-x+4=7`?

Answer 1

Since the second equation is only in `x`, we'll solve that first:

Explanation:

Subtract `4` from both sides:
`-x+cancel4-cancel4=7-4->`
`-x=3->x=-3`

Now substitute this `x`-value in the other equation:
`-3+3y=7`
Add `3` to both sides:
`cancel3-cancel3+3y=7+3->`
`3y=10->y=10/3=3 1/3`