The mean is the average of the numbers: a calculated "central" value of a set of numbers.
To calculate it: add up all the numbers, then divide by how many numbers there are.
Example: what is the mean of 2, 7 and 9?
Add the numbers: 2 + 7 + 9 = 18
Divide by how many numbers (i.e. we added 3 numbers): 18 ÷ 3 = 6
So the Mean is 6
hope you understood