Question 282223
Simply plug in {{{y=x}}} into {{{x+y=6}}} to get {{{x+x=6}}} (notice how I replaced 'y' with 'x'). Now solve {{{x+x=6}}} for 'x'. Once you have a solution in terms of 'x', use it to find the solution in terms of 'y'.


Note: in this case, the two solutions of 'x' and 'y' will be the same (since {{{y=x}}})