How do I find the mean difference in Statistics?

For Stat class, we have to find the prices of 20 items in 2 different stores, then find the mean difference. How do I find that exactly?

How do I find the mean difference in Statistics?
Find the average prices for the items from both stores, then see what their difference is.
Reply:its very easy, you add all the 20 items then divide them by 20 which are the numbers that you added, then the result will be the mean, and you do the same for the other store, then you look at the difference. heres a link that can help http://www.mathsisfun.com/mean.html