put all the combos together first like -3xy
then the x's like -x + 7x +2x=8x
then the y's
then the whole numbers
-3xy+8x (then the y's) then the whole numbers.
I am not sure how you are writing the numbers above like -x 4 is that -x to the 4th power?
x^4 then the x^3 and so forth then the y's then the whole numbers.
Always start adding the highest x power numbers first like x^4 + 2x^4=3x^4 then work your way down. Maybe rewrite the problem please.