I thought number 4 on this list was incorrect but didn't know how to fully explain it here is the list that I have.

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

1 answer

Line 4 is ok: 8x+3x = 11x
Line 5 is bogus. You cannot combine x,y,xy terms.

Line 4 is as far as you can go.