What set does 7.5 belong to?

Answer 1

To any set that contains it!

It belongs to {7.5},

or {7.5, sqrt(2), pi, -3/7},

or {7.5, bananas, France, cold}

or multiples of 2.5,

or halves of odd integers,

or rational numbers,

or real numbers,

or complex numbers,

etc.