Why, oh why, are we burdening the youth of today with the associative law of addition?
It is OBVIOUS !!!!!
Adding three numbers corresponds in a one-many way to putting three bundles of things in a bag, mixing them up (optional) and counting them. It would be a sad day if the count depended on the mixing.
This is an example of how far you have to go in abstract algebra to find a non-associative operation (and a fairly useless one at that)
No further comment from me !