1. **State the problem:** A boy bought 3 pairs of socks at 17.50 each and paid with two 50.00 notes. We need to find how much change he was given. 2. **Formula and explanation:** Total cost = price per pair \( \times \) number of pairs. 3. **Calculate total cost:** $$\text{Total cost} = 17.50 \times 3 = 52.50$$ 4. **Calculate total amount paid:** $$\text{Amount paid} = 50.00 \times 2 = 100.00$$ 5. **Calculate change:** $$\text{Change} = \text{Amount paid} - \text{Total cost} = 100.00 - 52.50 = 47.50$$ 6. **Answer:** The boy was given 47.50 as change. Therefore, the correct option is B. 47.50.