Earl is choosing a class ring. he can choose gold or silver, one of five different gemstones, and either a round or square stone. how many choices does he have?

What you can say is:

2 choices for the first one (metals)

5 choices for the second choice stemming off of all the possible first choices (gems)

2 choices stemming off of all those combinations (shape)

So basically it would be:

2 * 5 * 2 

Which is equal to 20.