The document provides steps for adding multi-digit numbers with regrouping. It explains that when adding numbers in columns, if the total in a column is 10 or more, you regroup by adding 1 to the column to the left and carrying the 1 to the next column. It then works through an example of adding 3,243 mathematics books and 4,659 science books. Finally, it provides additional practice problems for readers to try adding multiple multi-digit numbers themselves.