1. **State the problem:** Find the sum of 9 and 10. 2. **Formula used:** Addition of two numbers is given by $$a + b$$ where $a$ and $b$ are the numbers. 3. **Apply the formula:** Here, $a = 9$ and $b = 10$, so $$9 + 10$$ 4. **Calculate the sum:** $$9 + 10 = 19$$ 5. **Final answer:** The sum of 9 and 10 is **19**.