Answer: There are 9 different types of note cards that the store sells.
We can use the Fundamental Counting Principle to determine the total number of options.
There are two different events in this problem. First, there are 3 kinds of cards. Second, there are 3 sizes for each kind.
Simply, multiply the 3 by the other 3 and you have 9 different options.
Just think, each card would have a small, medium and larger option. So there are 3 groups of 3 or 9 total options.