This Application Problem is a part of the Lesson 7, Unit 1, Grade 2. Ricardo gave 5 tacos to his sister. He started with 13. How many tacos does Ricardo have left? This take from change unknown problem provides practice in recognizing that the missing part can be found by subtracting or adding on. A flexible understanding of the relationship of addition to subtraction and parts to totals is also necessary to use Level 3 strategies.