You don't have to regroup any of these problems: 23 35 46 65 29 - 1 - 2 - 3 - 4 - 5 --- --- --- --- --- 22 33 43 61 24 You DO regroup for these problems: 21 38 51 21 66 - 9 - 9 - 3 - 4 - 7 --- --- --- --- --- 12 29 48 17 59