Natural numbers.
1.18 is a number and number do not contain any sets (of any kind).
173 belongs to the set of positive natural numbers and it also belongs to the set of prime numbers.
There are approx 5.709*10^45 possible sets of numbers that can be made out of the composite numbers in 1 and 200.
You can select 12 numbers for the first digit, 11 numbers for the second digit, and 10 numbers for the third digit; so 12*11*10 = 1320 sets of 3 numbers can be made out of 12 different numbers.
Irrational Numbers which are a subset of Real Numbers which are a subset of Complex Numbers ...
Rational numbers
Among other things, it belongs to the following sets: positive numbers; irrational numbers; algebraic numbers.
It can be element of: Rational numbers or Real numbers
real numbers, irrational numbers, ...
Natural numbers.
10 belongs to the set "natural numbers", but it can also belong to whole numbers, and rational numbers
1.18 is a number and number do not contain any sets (of any kind).
17 belongs to the set of prime numbers
The rational numbers, the real numbers and sets of higher order which contain the reals such as the complex numbers.
A set is just a way of describing numbers, and numbers can be described in more than one way. If set A is (for example) all positive prime numbers, and set B is all numbers between 0 and 10, then there are some numbers (2, 3, 5, and 7) that could belong to both sets.
-28 belongs to: Integers, which is a subset of rationals, which is a subset of reals, which is a subset of complex numbers.