Final answer:
The number -11 belongs to the categories of Integers and Rational Numbers in the real number system.
Step-by-step explanation:
The number -11 is classified under the category of Integers. It does not belong to Natural Numbers or Whole Numbers because both of these sets include only non-negative numbers, whereas Integers include both positive and negative whole numbers, as well as zero. Since -11 is a whole number that is negative, it fits the definition of an Integer. Moreover, -11 also belongs to the category of Rational Numbers, because Rational Numbers include all numbers that can be expressed as the quotient of two integers (a fraction), where the denominator is not zero. Therefore, -11, which can be written as -11/1, is also a Rational Number.