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YOUR ANSWER: n = n says "any number is equal to any number."
You are correct. We defined n as meaning "any number." We gave no other rules or definitions. So far, then, all our statement n = n says is that any number equals any number. Such a statement is not even true, let alone useful. We must do better. We can accomplish a great deal by adding one simple rule. The rule is: If a letter stands for a number and is used in two or more places in a statement or equation, it stands for the same number in each place that it is used.
Now, with our new rule and the consequent modification of our definition of n, what does our statement n = n say?