Is(2x + 6x) + 4y + 3x - 2xy a correct simplification of an algebraic expression?

Question

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

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

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

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

d).Line 4: 11x + 4y - 2xy

e).Line 5: 13xy

Answer 1

Line 5 is wrong.  x, y, and xy are different things- different variables- so you can't just combine them like that.  Line 4 is the furthest you can go.