Answer:
19.2
Step-by-step explanation:
You get the mean of a set of numbers by adding them and dividing the sum by how many numbers there are. In this case, you don't know what the individual 8 numbers are, but you can find out what they add up to.
Mean = (sum) / 8
17 = (sum) / 8
17 x 8 = sum
136 = sum
Now take out the numbers 9, 11, 20, which reduces the sum by 40. There are 5 numbers left and they add up to 136 - 40 = 96.
The new mean is 96 / 5 = 19.2
