So to find average, we add up the values, and divide it by how many values there are in total.
27 + 12 + 31 + 19 + 23 + 11 + 17 = 140.
There are 7 numbers. Which means we divide 140 by 7.
140 / 7 = 20 is the average.
Also, if you notice, most of the numbers "kind of" circulate around 20.