Final answer:
The mode of the given set of numbers is 13.
Step-by-step explanation:
The mode is the value that appears most frequently in a set of numbers. To find the mode of a set of numbers, you can list the numbers in ascending order and look for the value that appears most often.
For the given set of numbers: 18, 13, 8, 8, 13, 10, 13, 10, 9, 18
The mode is 13 because it appears three times, which is more frequently than any other number in the set.