Addition of units requires two counts of units, the number of units to the left of the addition sign and the number of units to the right of the addition sign. This we say addition is a binary operation requiring two quantities. A single number can only be added to another number. It cannot be added to itself because it cannot be both itself and another. For example you can add six eggs to another six eggs and get 12 eggs altogether. However you cannot add six eggs to itself. Prove you can't add a number of units to itself.

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