Please consider the following expressions:

(a+b)+c
a+(b+c)
b+(a+c)

Let a, b, c be three ordinary numbers, like the prices of three items we wish to buy at the grocery store. The topic that I want to discuss (without doing it!) is that any three numbers have a unique sum. I think that the best way to describe this is to say the following: Pick two of the numbers, add them, and then add the third number. To show that any three numbers have a unique sum, we must prove that the result is always the same no matter how we pick the numbers, no matter what numbers we picked.

If we chain the expressions to the printed page - which includes the screen of an electronic device ... I mean, if we tacitly and implicitly ... and without really thinking about it ... treat the printed page as essential to the presentation of the topic, then the essential idea is obscured because of issues like whether we read from right to left or left to right, and "what do the parentheses mean?".

my e-mail: sunago.daviesb@gmail.com