In this lesson, students apply their place-value reasoning, mental strategies, and understanding of renaming to negotiate different problem types with unknowns in various positions. Students are guided through solving one- and two-step word problems. Next, they transition to solving problems on their own or with others. Students are encouraged to be flexible in their thinking and to use multiple strategies in solving problems in order to build fluency and further develop conceptual understanding of addition and subtraction using properties of operations and place-value reasoning.