Answer
$12_{{C}{_{4}}}$ = 495
Work Step by Step
TOTAL NUMBER OF BOOKS = 12
NUMBER OF BOOKS YOU WANT TO BRING ON VACATION = 4
THE NUMBER OF WAYS THAT THE 4 BOOK CAN BE CHOSEN OUT OF 12 = $12_{{C}{_{4}}}$
= $\frac{12!}{(12 - 4)! 4!}$
= $\frac{12!}{8!. 4!}$
= $\frac{12\times11\times10\times9\times8!}{8! 4\times3\times2\times1}$
= $\frac{12\times11\times10\times9}{ 4\times3\times2\times1}$
= 495
