Final answer:
The set {1, 2, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 16, 17, 19, 20} can be described as the set of all odd numbers in U.
Step-by-step explanation:
The set {1, 2, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 16, 17, 19, 20} can be described as the set of all odd numbers in U. To determine this, we need to look at the given sets A and B and determine which numbers in U are odd.
First, let's look at set A = {3, 6, 8, 12, 15, 18}, which contains 3, 15, and 18, which are odd numbers.
Next, let's look at set B = {1, 2, 3, 5, 8, 11, 15, 18, 19}, which contains 1, 3, 5, 11, 15, and 19, which are also odd numbers.
Since all the numbers in the given set {1, 2, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 16, 17, 19, 20} can be found in either set A or set B, it can be concluded that the set is the set of all odd numbers in U.