What are the sets of the real number negative 400?

Answer 1

They are all sets that contain it.

It belongs to {-400},

or {-400, sqrt(2), pi, -3/7},

or {-400, bananas, France, cold}

or all whole numbers between -500 and -300,

or multiples of 5,

or negative composite numbers,

or integers,

or rational numbers,

or real numbers,

or complex numbers,

etc.