How do I simplify the expression

8x+2x-3y-9x

X-3y because 8x+2x-9x is x

It's like adding and subtracting. All the ones with x's go together, and all the y's go together (or whatever other letters there are.) 8x+2x=10x

10x-9x=1x

1x=x (if there's a letter and the number next to it is 1 it is just the letter)

Now x-3y is your solution because x and y don't go together