These fact families need to be completed. Scholars use addition and subtraction to complete four number sentences for each set of three numbers. The sentences are all part of the number set's fact family, and demonstrate the commutative property of addition. They complete eight of these, and four from just a number pair. Next, scholars write out all four complete number sentences to form the fact families for four sets of numbers. Be sure to debrief the connection learners see between addition and subtraction, noting that multiplication and division will look very similar.