1. **State the problem:** Calculate the difference between 6.58 and 3.2. 2. **Formula used:** Subtraction of two decimal numbers: $$a - b$$ where $a=6.58$ and $b=3.2$. 3. **Align decimal places:** Write numbers as 6.58 and 3.20 to align decimals. 4. **Subtract:** $$6.58 - 3.20 = 3.38$$ 5. **Explanation:** Subtract the digits starting from the rightmost decimal place, borrowing if necessary, to get the final result. **Final answer:** $$3.38$$