Subtract two-digit numbers in columns - missing minuend or subtrahend

Students add the subtrahend and the difference column by column (ones first, then tens), looking for possible carries — the column structure organizes the inverse operation step by step.

Students may reverse the operation and subtract instead of add, especially if the missing value is in the middle position; explicit instruction on which inverse operation applies to each case prevents this.

Advanced worksheets include cases where the subtraction involved borrowing, requiring students to reason about the regrouping in reverse — a particularly challenging inverse operation application.