1. **State the problem:** Calculate the sum of 2 and 9. 2. **Formula used:** Addition of two numbers is given by $a + b$. 3. **Apply the formula:** Here, $a = 2$ and $b = 9$. 4. **Calculate:** $$2 + 9 = 11$$ 5. **Conclusion:** The sum of 2 and 9 is 11.