Question

If A = {3, 6, 9, 12, 15, 18}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12} and D = {5, 10, 15, 20, 25}, find:

C - D

Answer 1

{2   4   6   8   10   12} - {5   10   15   20   25   30} =    -3   -6   -9   -12   -15   -18

Answer 2

C-D means the elements which are present in C but not in D so the answer will be:
{2,4,6,8,12}