Differentiating both sides of

with respect to <em>x</em> yields (using the chain rule)

Solve for d<em>y</em>/d<em>x</em> :

The answer is then D.
1a. 5/10 can be simplified to 1/2. (5 divided by 5 is one, 10 divided by 5 is 2.)
1b. 9/12 can be simplified to 3/4. (9 divided by 3 is 3, 12 divided by 3 is 4.)
1c. 12/18 can be simplified to 2/3. (12 divided by 6 is 2, 18 divided by 6 is 3.)
1d. 9/24 can be simplified to 3/8. (9 divided by 3 is 3, 24 divided by 3 is 8.)
1e. 27/90 can be simplified to 3/10. (27 divided by 9 is 3, 90 divided by 9 is 10.)
1f. 40/48 can be simplified to 5/6. (40 divided by 8 is 5, 48 divided by 8 is 6.)
Mean is average. Multiply total books by the mean to find the total cost:
5x 10 = $50 total.
Subtract the highest and lowest prices to find the total of the remaining 3 books.
50 - 15-6 = 29
The median price was 8, this is the middle number, subtract 8 from 29 to get the cost of the last 2 books:
29-8 =21
Now you need a price lower than the median but higher than the lowest cost so that has to be 7
Subtract 7 from 21 to get the cost of the last book 21-7 = 14
The price of the remaining books is $7 and $14