The work of this lesson connects to previous lessons in which students solved Add To, Change Unknown; Put Together/Take Apart story problems with unknowns in different positions; and Compare, Difference Unknown story problems in a way that makes sense to them. In those lessons, students considered addition and subtraction equations that match the same story problem. In this lesson, students solve a variety of story problem types and compare strategies. Students explain how each of these problems can be represented or solved with addition or subtraction and relate subtraction to unknown addend problems.