Question

find the number of possible combinations choose one of three books and one of eight CDs to bring on a bus trip

Answer 1

There is a possibility of 24 combinations I believe

Answer 2

There are 3 possibilities when choosing 1 of 3 books.
There are 8 possibilities when choosing 1 of 8 books.
Events are independent of each other so "and" would be to multiply.
3 × 8 = 24 possible combinations

You can also see by writing out the possibilities..
Say names of books are {A,B,C} and names of CD's are {1,2,3,4,5,6,7,8}
A1, A2, A3, A4, A5, A6, A7, A8
B1, B2, B3, B4, B5, B6, B7, B8
C1, C2, C3, C4, C5, C6, C7, C8