What is the mean, median, and mode of 31, 28, 30, 31, 30?
The mean is the "average" - the sum of the values divided by the count of the values:
The median is the middle value in a string of values listed from lowest to highest (or highest to lowest - they just can't be scrambled up):
The mode is the value that is listed most often. In this case, both the 30 and 31 are listed twice, so they are both the mode.