Billy has enough money to buy 3 books. The books he can choose from include a poetry book, a mystery book, a biography, and a history book.
a. From how many different book is Billy choosing?
b. How many different combinations of 3 books are possible?
c. How many different combinations include the msytery books and the biograpy?
(a) just count the list -- 4 books!
(b) 4C3
Now what?