For a student skilled in addition, which subtraction algorithm is most appropriate?

Counting Up is the most appropriate subtraction algorithm for a student skilled in addition because it leverages the student's existing addition skills to simplify the subtraction process. This method involves starting from the smaller number (the subtrahend) and counting up to the larger number (the minuend), essentially finding the difference through addition. For example, if a student needs to calculate 7 - 5, they would start at 5 and count up to 7, which involves adding 1, 2 — leading them to realize that 7 - 5 equals 2.

This technique is particularly effective for students who have a strong foundation in addition since it transforms the subtraction problem into an addition one, thus making it easier to grasp while using familiar skills. In contrast, other algorithms such as Trade First or Direct Subtraction may require a different set of strategies or a greater understanding of borrowing and regrouping, which can complicate the process for those more comfortable with addition.