Here are the ways that five students thought about some addition facts. For each student, describe where each number in his or her thinking came from and why the strategy works. Then identify the basic fact strategy for addition being used by each of these students. (a) 9 + 5: Karen thinks, "Well, 10 and 4 more is 14." (b) 8 + 7: Donald states, "I know that 8 and 8 is 16, so one less is 15." (d) 4 + 8: Amber explains, "Eight and 2 more is 10, so 2 more gets me to 12." (d) 7 + 5: Roger says, "Five and 5 is 10, then 2 more is 12." (e) 7 + 5: Alison explains, "Seven and 3 more is 10, then 2 more is 12."