Answer:
A.) 18
Step-by-step explanation:
The mode is the number that occurs the most in the set, so it would be helpful to rearrange your numbers:
9
10
11, 11
12
13
15,15
18,18,18,18
From rearranging them, you can see that 18 occurs 4 times in the set, so 18 is the mode.
