PLEASE HELP ME WITH MATH (also please tell me how you got the answer so I understand)

Answer:
1st=3x+9, 2nd=8x, 3rd=4x+3y, 4th=neither, 5th=neither, 6th=4x+3y, 7th=3x+9, 8th=8x.
Step-by-step explanation:
for the 1st one cancel out the y's, 3x+9. for the 2nd one: 2x-1x+7x, (2-1+7)x, 8x. for the 3rd one: 2x+2y+2x+y, 4x+2y+y, 4x+3y. for the 4th one: 7x+x+0-y, 8x-y. for the 5th one: 2x+2y+2x, 4x+2y. for the 6th one: 4x+4y-y, 4x+3y. for the 7th one: 2x+6+x+3, 3x+6+3, 3x+9. for the 8th one: 5(2x)-2x, 5 * 2x-2x, 10x-2x, 8x.
Answer:
The answers would be :
first table (equivalent to 8x ) = 2x-x+7x , 7x+x+0×y , 5(2x)-2x
second one (equivalent to 4x+3y) = 2x+2y+2x+y , 4x+4y-y
third one = every expression left but 2x+2y+2x .
you have to calculate them ! for example look at the first one ----> y+3x-y+9 is equivalent to 3x+9 'cause y-y = 0 ,so 3x +9 will be the left expression and you can't calculate it because the both left items in expression are not from the same type , one of them has a x but the other one doesn't have .
or for example the second one is 2x-x+7x and you know that -x can be written as -1x ,so it becomes like 2x+-1x+7x = 8x .
in the above example we could calculate numbers 'cause all of them have the same variable .
hope it was kinda helpful , sorry for bad english :D
ask me if you have further questions .