Please look at the following simplification of an algebraic expression. Which line contains the mistake and why?

Line 1: (2x + 6x) + 4y + 3x - 2xy

Line 2: (8x) + 4y + 3x - 2xy

Line 3: 8x + 3x + 4y - 2xy

Line 4: 11x + 4y - 2xy

Line 5: 13xy

line 5 is the one that is different. No x term and no y terms , just x y term