This is a great activity to do once you have taught how to find the domain, range, and determining functions. I used it as a warm-up after the lesson had been taught. You give each student a set of the cards (I recommend copying them on different colors of paper, that way they aren't as easy to get mixed up). The first thing you can do is have the students seperate them into 2 columns, 1 for functions, the other for nonfunctions. Once they have them seperated, you can have them find the domain and range of each function.
I made it for my Algebra 2 class, but I also used in my Pre-Calc class as a warm-up one day before we reviewed those topics. It gave me a good idea of what the students knew before I went into my notes.