1. **State the problem:** Calculate the sum of 3 and 5. 2. **Formula used:** Addition of two numbers is given by $a + b$. 3. **Apply the formula:** Here, $a = 3$ and $b = 5$, so we calculate: $$3 + 5$$ 4. **Perform the addition:** $$3 + 5 = 8$$ 5. **Final answer:** The sum of 3 and 5 is 8.