Question 562838
Hi, the system you gave has infinitely many solutions (any choice of x and y works).  Here is a system with no solutions,
x+y=8
-x-y=-7
Proof:
Suppose there exists a solution pair, call it x,y.  Then the equations are satisfied i.e. x+y=8 and -x-y=-7.  Add the equations to get 0=1.  But this can't be true, so there is no solution pair to the system by contradiction.