Let's define the sets based on the information given:

1. Set $U$: The universal set consists of all whole numbers from 0 to 20.
   $U = \{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20\}$

2. Set $X$: This set consists of whole numbers less than 10.
   $X = \{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\}$

3. Set $Y$: This set consists of whole numbers greater than 5 but less than 20.
   $Y = \{6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19\}$

4. Set $Z$: This set consists of whole numbers between 4 and 11 (including 4 and 11).
   $Z = \{4, 5, 6, 7, 8, 9, 10, 11\}$

Would you like to perform specific operations with these sets, such as union, intersection, or difference?

Here are 5 follow-up questions related to set theory:

1. What is $X \cup Y$ (the union of sets $X$ and $Y$)?
2. What is $X \cap Y$ (the intersection of sets $X$ and $Y$)?
3. What is the complement of set $Z$ with respect to $U$ (denoted $U - Z$)?
4. How many elements are in the union of all three sets $X$, $Y$, and $Z$?
5. What is the symmetric difference between sets $X$ and $Z$?

Tip: The union of two sets contains all distinct elements that are in either set, while the intersection contains only elements that are in both sets.