"Mean" is really the average on a set of numbers. The video uses the temperatures on a weather report as an example of a data set. Start by adding the temperature numbers of the week up. After you have the total, divide that number by 7, because you used 7 numbers in your data set. The answer that you get after dividing will have a few decimal places at the end of it. You can round the answer to the nearest whole number because all the numbers from your original data set do not have any decimals on them. That number will be the mean for you data set, or in this scenario, the mean temperature for the week.