The first number, x, is 3.5. The other number, y, is 10.5. X+y=-7 X-y=14. Those are the two equations. If you use the elimination method, and add those two equations together, the resulting equation is 2x=7. That means the first variable is 3.5. So, 3.5-y=-7, so that means y is -10.5. If you plug that in with the other equation then it comes out as true.