Question

How just how do you do this?

Answer 1

You need to get y alone for both equations. for x-y=7, you subract x from both sides. (giving you -y = 7 - x) then, multiply the whole equation by -1 to make the y positive, which gives you y = x - 7.
here is the system in y intercept form so you can graph it easier:
*y = x - 7
*y = x + 4