1. **State the problem:** Calculate the sum of 10 and 10. 2. **Formula used:** Addition of two numbers is given by $a + b$. 3. **Apply the formula:** Here, $a = 10$ and $b = 10$, so we calculate $10 + 10$. 4. **Perform the addition:** $10 + 10 = 20$. 5. **Conclusion:** The sum of 10 and 10 is 20.