Question

For the following system, if you isolated x in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

-x + 2y = 9
4x + 5y = 9

Answer 1

It said to isolate x in the first equation. So subtract 2y from both sides:
-x = -2y + 9
Now multiply by -1 (because we want x and not -x) and get x = 2y -9

Answer 2

And that is the expression you would substitute into the second equation in place of x