I believe you are asking, in math, what is a mean. Mean is just another way of asking for the average. To find the mean you simply add the numbers in the set together and divide the the number of items. For example, in the following set of numbers, 18.104.22.168.7.8..21 and 34, there are 8 items. The sum of these numbers is 87. 87 divided by 8 is 10.875, so the average (or mean) of this set of numbers is 10.875.