Column Addition and Column Subtraction: For large numbers, align digits vertically by place value, and start adding or subtracting from the rightmost column.

(0:50)Carrying Over in Addition: When the sum in a column is more than one digit (e.g., 10 or 12), carry over the “1” to the next column.

(2:06)Borrowing in Subtraction: When the top digit is smaller than the bottom digit in a column, borrow “1” from the next column.