I've tried them out, with the following answers:-
(i) A = {2,4,6,8,10,12,14,16,18,20}, Therefore A has a cardinality of 10 (elements).
(ii) B = Cartesian Product of 'X times X times Y' or better yet '4 by 4 by 3' elements each to give a total of 48 in cardinality?!
(iii) C = UNSOLVED!
I...