The correct answer is 309 because when you subtract 348 from 657, you subtract the ones place first, which gives you 7 - 8. Since 7 is smaller than 8, you need to borrow 1 from the tens place, which leaves you with 16 - 8. This gives you an answer of 8. Then you subtract the tens place, which gives you 5 - 4, which is 1. Finally, you subtract the hundreds place, which gives you 6 - 3, which is 3. Therefore, the final answer is 309.