Answer: 17160
Explanation:
first there are 13 options
then there are 13 - 1 that was chosen
then there are 13 - 2 that were chosen
then there are 13 - 3 that were chosen
so that's 13 options, then 12 options, then 11 options, and then 10 options
and in order to figure out all of the possibilties we mutiply the options so
13*12*11*10 = 17160
little further explaining of why this works:
we have a set of letters (3 in a set)
A B C
what are the possible combinations?
AB
AC
BC
BA
CA
CB
the answer is 6 which is also 3 * 2 * 1 = 6