Question

Prove that every set is a set of itself .

Answer 1

By definition, set X is a subset of set Y, if every element of set X is element of set Y.
Now, every element of set A is an element of set A.
Therefore, set A is subset of set A.
Hence, every set is a subset of itself.

Disclaimer: Question should have been "Prove that every set is a subset of itself" instead of "Prove that every set is a set of itself".