part A
if the paperbacks are 40% less, that means 100% - 40% = 60%, they actually are 60% of the price of the hardcover ones.
part B
so, if they return it, they get 1/3 credit, if they try to sell it, is half off, which is more than 1/3. 22 got damaged.
part C
I don't think she is incorrect, $17.5 is close to $20, she didn't say it was exactly $20, just thereabouts, and 17.5 is around that much.
Very nice handwriting but the math and English are confusing.
Let's assume we're told
The subscript is important.
I think we're told the similar sum with 11 gives the smallest possible value for the sum. This is a rather cagey way of telling us 11 is the mean of the nine points. The mean is the number which minimizes the sum of squared deviations.
If 11 is the mean, the sum of the points is 9(11)=99.
Answer: 1080