You've learned how to work subtraction problems with two and three digits. You can­ subtract with and without regrouping (borrowing). You've also practiced regrouping hundreds to t­ens by rewriting digits.

Now check this problem out:

Here you'll use regrouping more than once. Let's find out why.

Look at the ones place. There's 6 on top and 8 on the bottom. In the tens place, 4 is on top and 5 is on the bottom. Notice that both place values begin with the lesser (smaller) numbers. (You will sometimes see the terms "ones column" and "tens column" used.)

What does this mean? In the ones place, you have 6 minus 8. In the tens place, it's 4 minus 5. Can you work directly with these numbers? No. The lesser number is on top. You need to regroup first.

Underline the digits you need to rewrite for regrouping.

Which do you rewrite first? You must rewrite the 4 first. Remember, you must regroup from the tens place to change 6 to a two-digit value that you can subtract 8 from. So write the 1 you borrowed in the ones place to make the new number, 16. Then cross out the 4 and write 3.

Next, rewrite the hundreds digit. Cross out the 9 and write 8. Then write the 1 you regrouped in the tens place to make the new number, 13.

We can now go back to the problem 946 minus 558.

The problem in the ones place is now 16 minus 8. The difference (answer) equals 8. In the tens place, it's 13 minus 5, which equals 8. In the hundreds place (hundreds column), you solve 8 minus 5 equals 3. Here's how it looks using column subtraction:

Now you're ready for more challenging subtraction problems.