To any set that contains it!
It belongs to {1.18},
or {45, sqrt(2), pi, 1.18, -3/7},
or all numbers between -2 and 453,
or improper fractions (1.18 = 19/50],
or rational numbers,
or real numbers,
or complex numbers,
etc.
No. One, a counting number, doesn't belong to either of those sets.
The complex numbers.
Counting numbers
There are two sets of numbers listed at the bottom of a check. These sets of numbers are the routing numbers and the account number. The nine digit set of numbers is the routing number.
It belongs to any set that contains it: for example, {4.75, -12, pi, sqrt(5), 29}. It belongs to the set of integers which is a proper subset of rational numbers which is a proper subset of real numbers which is a proper subset of complex numbers. So -12 belongs to all the above sets.
Rational numbers
There are no sets of three consecutive numbers totaling 118.
real numbers, irrational numbers, ...
Natural numbers.
It can be element of: Rational numbers or Real numbers
1.18 is a number and number do not contain any sets (of any kind).
17 belongs to the set of prime numbers
Irrational Numbers which are a subset of Real Numbers which are a subset of Complex Numbers ...
The rational numbers, the real numbers and sets of higher order which contain the reals such as the complex numbers.
-10 belongs to the set of all integers denoted by Z.
-28 belongs to: Integers, which is a subset of rationals, which is a subset of reals, which is a subset of complex numbers.
173 belongs to the set of positive natural numbers and it also belongs to the set of prime numbers.