..how many possible 5 digit zip codes are there if numbers can't be repeated? Mr F says: (10)(9)(8)(7)(6) = ...... if a zip code can start with 0, (9)(9)(8)(7)(6) = ...... otherwise.

how many ways can 7 different items be arranged in a single line? (is that 7 factorial?) Mr F says: Yes.

how many ways can i select 5 different objects out of 12 objects total? Mr F says: