Mean is the same thing as average, so to find this you would add all of the numbers together and divide them by the amount of numbers you added. For example, (6+9+11)/3
Median is the middle number of the list of numbers, but you have to put them in numerical order first. If there is not an exact middle, you would add the middle two together and divide by two.
Mode is the number that occurs most often within the list of numbers.