1. The problem is to add two numbers that have the same digits. 2. When digits are the same, adding them is straightforward: you add each digit in the same place. 3. For example, if the numbers are $123$ and $123$, then adding them digit by digit gives: $$1 + 1 = 2$$ $$2 + 2 = 4$$ $$3 + 3 = 6$$ 4. So, the sum is $246$. 5. In general, if the digits are the same, the sum is each digit doubled, taking care of carrying if needed.