How do you use variable in an addition or subtraction?

Answer 1

well, if you want to add apples to bananas you can't do that

it's the same with variables, the coefficients can be different but to add and subtract the variables have to be the same for ex:

you can't do 4x+3y because they have different variables

you can do 4x+3x because they have the same variables all you do is add the coefficients and keep the variable so you would get 7x