Answer:
Assuming you have a set of numbers:
The mean can be found by combining all the numbers in the data set, and dividing by the amount of numbers that are in the set.
The median can be found by, after rearranging the numbers in the data set to least to greatest (if it isn't already), the middle number will be the median. If there is a even amount of numbers in the given data set, you will take the two middle numbers and find the mean of the two.
If you want to know the others:
The mode is the number that shows up the most within the data set.
The range is the number that is obtained by subtracting the least valued number from the greatest value number.