How do you find the mean? You add the numbers up and divide by the amount in the set. So, we have to go backwards. Since we divided, we need to multiply 4 by 22. You get 88. Now add that new number of 18 to 88 to get 106. Now there are 5 numbers in the set so you divide 106 by 5 to get 21.2. So the answer is C. 21.2! Hope this helps!