If you have a bunch of unparenthesized addition and subtraction, left to right is correct
If you have a bunch of unparenthesized addition and subtraction, left to right doesn't matter.
1 + 2 + 3 = 3 + 2 + 1
If you have a bunch of unparenthesized addition and subtraction, left to right doesn't matter.
1 + 2 + 3 = 3 + 2 + 1