Determine the number of ways a 7-digit number can be formed from 7 digits, given
that each digit can NOT be used more than once.
Given we have 7 digits to choose from, we have 7 options for the first digit, which leaves 6 for the second, 5 for the third, and so on.
Hence, the number of possible 7-digit numbers we can form from 7 different numbers without replacement is .
This can be written as .