Rational
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.
-5
-12 belongs to negative integers
To any set that contains it! It belongs to {12}, or {12, sqrt(2), pi, -3/7}, or all whole numbers between 3 and 53, or multiples of 3, or composite numbers, or counting numbers, or integers, or rational numbers, or real numbers, or complex numbers, etc.
it belongs to group 12 or IIB
the range belongs to the set of real numbers and is infinite since the equation describes a straight line.
The two main DISJOINT subsets of the Real numbers are the rational numbers and the irrational numbers.
12
belongs to an infinite number of sets. For example, the Real Numbers, the Rational Numbers, Integers, negative integers, odd negative integers, negative primes numbers, the set {12, -17, 98} or {2.76, pi, -17, k, wikianswers}. In fact any collection, however random, of numbers or other things, that includes -17.
zinc, cadmium, copernicum. (not counting F-Block)
It belongs to many many subsets including: {sqrt(13)}, The set of square roots of integers The set of square roots of primes The set of square roots of numbers between 12 and 27 {3, -9, sqrt(13)} The set of irrational numbers The set of real numbers
There is no pair of real numbers. In the complex field, there is the pair: -1.5 - 3.1225*i and -1.5 + 3.1225*i where i is the imaginary square root of -1. Alternatively, in real numbers, you have a set of 12 numbers : 3*4*(-1)10