6x + 7y - 7 (1)
By the way, I'm assuming that the above is a typo, and that the "minus" sign is supposed to be an "equals" sign.
6(x=6-7y) + 7y -7
Please review the lesson (provided in the link, earlier) and re-read the instructions in the previous reply. You are not supposed to plug the entire second equation in for the one variable; you are supposed to "substitute" the expression that "x=" (that is, the expression on the other
side from "x") in for "x" in the first equation, so that you have only one variable, not two, and only one "equals" sign.