You have to substitute the equation. sub y=1x-1 into the other equation.

-y = x-1 is a fairly simple equation at least with real integers.

I hope to help you understand the process of solving it so you can apply the thinking to increasingly difficult equations. If this equation is difficult for you, I will try to explain it simply.

let's try a simple trick. If you want to solve for y, then it's helpful to remove the negative from it.

that means you need to do the same thing to the x side, but since x is already positive it needs to change to -x to balance things out.

the equation now reads y = -x+1 because we have reversed the negative and positive values on both sides of the equation.

I hope this helps simplify the thinking behind solving an equation of this nature. The two previous answers above this one are both correct, but may be just a tad more complex than you need at this moment.