How many 3-digit numbers can be made using the digits 1 5 7 4 6 if you can only use each digit once in ever number?

You have 5 choices for the 1st digit of the number.

4 choices for the 2nd digit and 3 choices for the 3rd and final digit.

This means that there are 5 x 4 x 3 = 60 3-digit numbers that can be made from 5 different digits subject to each digit only being used once.