Question 142804

{{{x + y = 3}}}  and  {{{y = x + 3}}};
 you can write them both in the standard form like this:

 {{{x + y = 3}}}  
{{{-x + y = 3}}}

*[invoke solving_linear_system_by_substitution 1, 1, 3, -1, 1, 3]