Question

Marty bought 4 new books today. He plans to read 2 of these while on vacation. How many combinations of 2 books from the group of 4 could he choose to read?

Answer 1

There are 6 different combinations of 2 books from the group of 4 that he could choose to do.

Let's say all of the books were letters.
Books a, b, c, and d.

Different combinations include:

ab, ac, ad, bc, bd, and cd.