This Instructional Activity is a part of the Lesson 9, Unit 4, Grade 8. In Module 1, you saw the following problem: You sent a photo of you and your family on vacation to seven Facebook friends. If each of them sends it to five of their friends, and each of those friends sends it to five of their friends, and those friends send it to five more, how many people (not counting yourself) will see your photo? Assume that no friend received the photo twice. In Module 1, you were asked to express your answer in exponential notation. The solution is given here.