This Problem Set is a part of the Lesson 2, Unit 1, Grade 7. Students understand that two quantities are proportional to each other when there exists a constant (number) such that each measure in the first quantity multiplied by this constant gives the corresponding measure in the second quantity. When students identify the measures in the first quantity with with 𝑥 and the measures in the second quantity with 𝑦, they recognize that the second quantity is proportional to the first quantity if 𝑦 = 𝑘𝑥 for some positive number 𝑘.