You can put this solution on YOUR website! x – y = 3
-y=-x+3
y=x-3 (red line)
-6x + 6y = 17
6y=6x+17
y=6x/6+17/6
y=x+17/6 (green line) (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions x -3 and x +17/6).
As you can see these two lines are parallel thus there is no unique solution for x or y.