Let the given sets are A={3,6,12,15,18,21}, B={4,8,12,16,20}, C={2,4,6,8,10,12,14,16} and D={5,10,15,20}. Find A – C.

Hint: We are going to use the idea of finding differences between two sets.

Complete step-by-step answer:
Four sets are given as follows.
A = {3, 6, 12, 15, 18, 21}
B = {4, 8, 12, 16, 20}
C = {2, 4, 6, 8, 10, 12, 14, 16}
D = {5, 10, 15, 20}


We need to find the difference set A – set C.
$ \Rightarrow $ A – C = {3, 6, 12, 15, 18, 21} – {2, 4, 6, 8, 10, 12, 14, 16}
A – C represents a set which contains all elements of A that are not elements of B.
A-C = {3, 15, 18, 21}


Note: If x and y are two sets, the difference of set y from set x, denoted by x – y is the set that contains elements which present only in set x not in set y. The differences x – y and y – x both are different.