Total no of subsets=2n=24=16
Here n is the Cardinal no of the Given Set
Given A={1,2,3,4} and B={4,5,6,7}
A-B set will contain those elements which are present in A but not in B
we can see A∩B={4}
Now A−B=A−(A∩B)
so A−B={1,2,3,4}−{4}={1,2,3}