The given sets are U={4,8,12,16,20,24,28}, A={8,16,24} and B={4,16,20,28}
We know that the complement of set A is A′=U−A.
Consider the following:
(A∩B)′=U−(A∩B)={4,8,12,16,20,24,28}−[{8,16,24}∩{4,16,20,28}]
={4,8,12,16,20,24,28}−{16}={4,8,12,20,24,28}......(1)
A′∪B′=[U−A]∪[U−B]=[{4,8,12,16,20,24,28}−{8,16,24}]∪[{4,8,12,16,20,24,28}−{4,16,20,28}]
={4,12,20,28}∩{8,12,24}={4,8,12,20,24,28}......(2)
From equations 1 and 2, we get that (A∩B)′=A′∪B′.
Hence, (A∩B)′=A′∪B′.