Answer:
[see below]
Explanation:
The Mean:
Add all values together:

There are 8 numbers in the data set.
40 ÷ 8 = 5
The mean of the data is 5.
The Median:
Order the numbers in ascending order.
4, 4, 4, 4, 5, 5, 6, 8
There is no exact middle number.

The median of the data is 4.5.
The Mode:
'4' appears the most in the data set.
4, 4, 4, 4, 5, 5, 6, 8
The mode of the data is 4.