Use this assessment question which aligns with CCSS: HSF-BF.A.1: Build a function that models a relationship between two quantities. Which teaches students about how to build a function which shows a relationship between two students who are saving up to go Comic Con!
This question asks students to read a problem, find the functions that the problem describes, and then to answer questions relating to their functions in order to make connections between the qualities. Such as being able to graph the functions and find which graph is increasing faster, find the point of intersection, and interpret how changes to the functions can affect the function slopes and point of intersection.