Algebra studies groups.
Group's binary operation is associative.
The order of calculations is irrelevant for an associative operation.
That's why you've never read about "L-to-R" and "R-to-L" order in algebra books.
If operation is commutative, it might be referred to as "multiplication",
and "division by x" is defined as "multiplying by the inverse of x".
So, in the absence of parentheses
a/b/c = a * b^(-1) * c^(-1)
by the definition of division.
I NEVER heard of a left to right execution rule in math (only in programming), not at school, not at university.
You should definitely have learned it in school.
Have you never seen such pictures in your math class?
