Chapter 2 - Set Theory - 2.2 Subsets - Exercise Set 2.2 - Page 68: 25

{x|x is a man} ⊂ {x|x is a person}

The first set is a proper subset of second set because a man is always a person, but a person need not become a man..so they are not equal sets. Therefore {x|x is a man} ⊂ {x|x is a person}