The answer is 6.
Step-by-step explanation:
Since the question is asking for the number of suspensions, we'll only look at the left part of the chart.
The formula for mean is all the numbers added up in the set divided by the amount of numbers.
So, in this problem, we add up 4,5,6,7 and 8 which equals 30, and divide by 5 to get 6.