Robust Mirror

It’s so we don’t have to spam brackets everywhere

9+2-1+6-4+7-3+5=

Becomes

((((((9+2)-1)+6)-4)+7)-3)+5=

That’s just clutter for no good reason when we can just say if it doesn’t have parentheses it’s left to right. Having a default evaluation order makes sense and means we only need parentheses when we want to deviate from the norm.

Another person already replied using your equation, but I felt the need to reply with a simpler one as well that shows it:

9-1+3=?

Subtraction first:
8+3=11

Addition first:
9-4=5