The mode of a data set is the number that occurs more frequently. For this question, data set is:
If you count how many times each number appears, you will find that 11 apears 3 times, then 14, 13 and 10 appear 2 times each, and the rest only once.
So, in this set of data, the mode is 11, since is the value that occurs more frequently.
A set of data can have more than two modes. If 14 appears 3 times as well, then the mode of this data set will be 11 AND 14.
The best way to find the mode is to write all numbers in order, so you'll find more quickly how many times they occur.