Answer: The mean is 17, the median is 17, and the mode is 18.
Here's an explanation of how to find each.
Mean: When finding the mean, you must add together all the values, then divide by the total number of values stated. So, adding all the numbers together will give you 187. The divide by 11 (since there are 11 numbers) to get a mean of 17.
Median: When finding the median, simply put the numbers in numerical order, and find the the number in the direct middle. The numbers in numerical order are 12, 14, 14, 16, 17, 17, 18, 18, 18, 20, 23, making the median 17.
Mode: The mode is the number that shows up most often (most frequently). Since 18 shows up most (3 times) withing the data, it is the mode.
I hope this helps!