This Instructional Activity is a part of the Lesson 3, Unit 3, Grade 7. Students use area and rectangular array models and the distributive property to write products as sums and sums as products. Students use the fact that the opposite of a number is the same as multiplying by -1 to write the opposite of a sum in standard form. Students recognize that rewriting an expression in a different form can shed light on the problem and how the quantities in it are related.