This Instructional Activity is a part of the Lesson 21, Unit 6, Grade 7. In this activity students continue the work of generating equivalent expressions as they decide where to place a set of parentheses and explore how that placement affects the expressions. Arrange students in groups of 2. Tell students to first complete both questions independently. Then, trade one of their expressions with their partner. The partner's job is to decide whether the new expression is equivalent to the original or not, and explain how they know.