What is this "order of operation" cult now with math?

[Vtile]

I must disagree. The sole reason is the 1st axiom of real number algebra (and therefore also aplying to subsets) and the distributive theorem and how the convention is to mark the common factor without operator to parentheses (as is done with ie. exponentation) that is to interpret the whole right side notation in this case as a one object as '(a(X+Y))'.

Can't say what is thought for me been under too many influential teachers and institutions along the years. As in Finland.