Students work with the standard algorithm for subtraction in Topic E. As in Topic D, they use two- and three-digit metric measurements and intervals of minutes within 1 hour to subtract. The sequence of complexity that builds from Lessons 18–20 mirrors the progression used for teaching addition. In Lesson 18, students begin by decomposing once to subtract, modeling their work on the place value chart. They use three-digit minuends that may contain zeros in the tens or ones place. By the end of the lesson, they are less reliant on the model of the place value chart and practice using the algorithm with greater confidence.