Ok so that makes it a permutation problem of type 'with replacement' instead of a combination problem?
A related question has got me stuck again.
(b) How many of the sequences in part (a) will contain three picture cards, three odd-numbered cards and two even-numbered cards.
Note: (a) was the original question, i.e., "How many different sequences of eight cards are possible?"
I do really have a trouble with permutations and combinations, so a little explanation in this answer will be greatly appreciated.
So points that I have noticed: (please correct if mistaken)
* There are 3 types of objects
* There are 8 objects to be selected out of the 3 types