Question 151271
If you use elimination and the resulting equation makes 'no sense' then there is no solution. For instance, if you do the subtraction/addition and the answer is something like 0 = 14, then you know there is no answer

Likewise if the resulting equation turns out to be 0=0 or something like that, then there are infinitely many solutions. Another way to see if there are infinite solutions is to "see" then the second equation is just a simple multiple of the first one.