Answer
Please see below.
Work Step by Step
Consider the problem:
Suppose that there are $7$ different books on the shelf. How many ways can one select $3$ of them, assuming that the order of the selections makes a difference?
Answer:
We can solve this problem with permutations:
$P(7,3)=\dfrac{7!}{(7-3)!}=\dfrac{7!}{4!}=\dfrac{7*6*5*4!}{4!}=7*6*5=210$
Thus, there are $210$ ways to choose the books.
