Concept 1. The null set is a subset of every set. (φ⊂eqA ) 2. Every set is a subset of itself. (A⊂eqA ) 3. The number of subsets of a set with n elements is 2n. Explanation: 1. The null set is a subset of every set - The intersection of two sets is a subset of each of the original sets. So if {} is the empty set and A is any set then{} intersect A is {} which means Z{} is a subset of A and {} is a subset of{} . You can prove it by contradiction. Let's say that you have the empty set {} and a set A. 2. Every set is a subset of itself. (A⊂eqA ) 3. If n=10 then 210=1024 So, all three statements are true.