mathalg
posted by Anonymous on .
8. In how many ways can 12 books be displayed on a shelf if 15 books are available?: *
A. 455
B. 479001600
C. 2.17945728 x 1011
D. 2730

This is a permutation. I searched Google under the key words "permutations math" to get these possible sources:
http://mathforum.org/dr.math/faq/faq.comb.perm.html
(Broken Link Removed)
http://www.wtamu.edu/academic/anns/mps/math/mathlab/col_algebra/col_alg_tut56_perm.htm
Perhaps this information will help. Thanks for asking.