To regroup, you simply break up the bigger numbers into smaller numbers that are more easily added together. We often regroup into numbers that end with 0 because they're easier to add. For example, you can break up 64 into 60 + 4 and 43 into 40 + 3. This will make addition easier, because you can first add together 60 and 40, which will equal 100. Then, you can add the smaller digits: 100 + 4 + 3 = 107.
