This Application Problem is a part of the Lesson 18, Unit 4, Grade K. This story introduces the thinking for the put together with both addends unknown problem structure in today's lesson. In this lesson, students work with addition stories where both addends are unknown (C = ___ + ___). This work is based on an original work of Great Minds and licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.