If U = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, A = {3, 5, 7, 9, 11} and B = {7, 8, 9, 10, 11}, Then compute (A – B)′.

A – B is a set of member which belong to A but do not belong to B
∴ A – B = {3, 5, 7, 9, 11} - {7, 8, 9, 10, 11}
A – B = {3, 5}
According to formula,
(A − B)′ = U - (A – B)
∴ (A − B)′ = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11} - {3, 5}
(A − B)′ = {2, 4, 6, 7, 8, 9, 10, 11}.