The opposite operation to addition is subtraction and vice versa. In this worksheet, students apply this relationship and their knowledge of basic addition and subtraction facts to add and subtract 5-digit and 4-digit numbers without regrouping. In this worksheet, students practice solving problems written in the horizontal format. How numbers are laid out in a problem affects the method a student employs to solve it. Therefore to develop actual fluency and mastery of multiple strategies, students must practice different formats.