1. **State the problem:** Calculate the product of 7 and 3. 2. **Formula used:** Multiplication of two numbers $a$ and $b$ is given by $a \times b$. 3. **Apply the formula:** Here, $a=7$ and $b=3$, so we calculate $7 \times 3$. 4. **Intermediate work:** $$7 \times 3 = 21$$ 5. **Explanation:** Multiplying 7 by 3 means adding 7 three times or 3 seven times, which results in 21. 6. **Final answer:** $$\boxed{21}$$