A function is a rule that takes an input, does something to it, and gives an output. Each input has exactly one output.
It is often helpful to think of a function as a box.
The box (the function) can be labeled with what it does. 
CONCEPT QUESTIONS EXERCISE:
On this exercise, you will not key in your answer.However, you can check to see if your answer is correct. 
PROBLEM TYPES:
