Answer:
a. They are empty set.
b. they are finite set.
Solution,
a. A={ prime number between 6 and 7}
There are not any number between 6 and 7.
So there will be no Elements.
A={ }
It is empty set.
Empty set are those set which doesn't contain any Element.
b.B={multiples of 2 less than 20}
B={2,4,6,8,10,12,14,16,18}
It is a finite set.
Finite set are those set which we can count easily.
Hope this helps...
Good luck on your assignment...