Answer:
x+14y-18xy
Step-by-step explanation:
1) Multiply terms if needed.
2) Group your terms by variables. (x with x, y with y, xy with xy, etc.)
3) Add like terms (terms with same variables)
This problem will look like:
Step one: take the term "-2y9x" and multiply to creat one term (You have to remember PEMDAS with these problems. Look it up if you don't know what it is :) ) You should come up with -18yx for this term.
Step two: Organizing terms ---> 9x-4x-4x+8y+8y-2y-18xy
Step three: Take your like terms and add them together. Your answer should end up being x+14y-18xy