Answer:
The rate of change for each reader is :
For J K Rowling :  17 and a half pages per hour
For R L Stone :  15   pages  per hour
Step-by-step explanation:
Here the reading rate of each reader is given as:
J.K. Reads 35 pages every 2 hours.
So, the number of pages read by J K  in 2 hours  = 35 pages
⇒ The number of pages read per hour  =  35 / 2  = 17 . 5 pages
So, the pages read by J K Rowling in 1 hour is 17 and a half pages.
R L Stone reads 45 pages every 3 hours.
So, the number of pages read by R L  in 3 hours  = 45 pages
⇒ The number of pages read per hour  =  45 / 3  = 15 pages
So, the pages read by R L Stone in 1 hour is 15 pages.
Hence, the rate of change for each reader is :
For J K Rowling :  17 and a half pages  per hour
For R L Stone :  15   pages  per hour