Aday care facility is open six days a week . the numbers of children who attend each day are 22,23,23,24,20,8 what is the most appropriate measure of center

In this data set, the number 8 is an outlier.  An outlier is a value that is far away from the rest of the numbers (either a lot smaller or a lot greater).

Because there is an outlier, the measure of center that best represents the data would be the median (the middle value).  The mean will not be accurate because the outlier will make it smaller than what is actually being represented in all of the numbers but one.