I hate being unsure about these things but I don't want to get in a habit of doing it wrong.

Here's an example:

9 + 2y + x - 25 + 3 + x

In using the commutative property, when I move stuff around, is there a rule as to which order it should be in? If I arbitrarily move things around I'll end up with different solutions, obviously.

So, if a constant comes first, a 'y' monomial second, and an 'x' variable third, should I move all the constants up, then the 'y' monomials, followed by the 'x' variables?

9 - 25 + 3 + 2y + x + x

According to PEMDAS, I should do addition before subtraction. So, the associative step would look like this:

9 - (25 + 3) + 2y + (x + x)

Or should I just go in order: (9 - 25) + 3 + 2y + (x + x)