"1 + 1 = 2" has a commonly understood meaning that implies a system of axioms and theorems and whatnot so as to be an objectively true statement in that context

"1 + 1 = 2" has a commonly understood meaning that implies a system of axioms and theorems and whatnot so as to be an objectively true statement in that context. You're not being asked to interpret what someone means by "1 + 1 = 2"; you're being asked to examine that string of characters in the context of a specific system that you clearly understand.