sets and subsets

[Bart Nessux]

By using lists, I can create sets of number. Suppose I have three lists. 
One list is the super-set, one is a set that contains all the numbers 
(just like the super-set) and the last is sub-set of the super-set. For 
example:

a = [1,2,3,4,5]	# The super-set.
b = [1,2,3,4,5] # Looks just like the super-set, but it's not.
c = [2,4]	# A sub-set

I'd like to remove 2 & 4 from set b BECAUSE they are present in set c... 
this would make the sets look like this:

a = [1,2,3,4,5]
b = [1,3,5]
c = [2,4]

How do I test set c to find what it contains and then look at set b to 
see if it contains any of those same numbers, and if so, remove them.