Given that a certain antihistamine is often prescribed for allergies.
And typical dose for 100-pound person is 25 mg every 6 hours.
a) Let us calculate dose per 1 hour for 100-pound person= 
Since 1 week means 7X24= 168 hours, dosage per 1 week = dosage per 168 hours

The number of 12.8 chew able tablets would be taken in a week= 
Hence number of 12.8mg chew able tablets would be taken in a week is 55.
b) Now we can use earlier answer for this problem, since 12.8mg tablet is replaced with 9ml liquid, 55 bottles of 9ml liquid are to be taken in a week.
Hence amount of liquid histamine should a 100-pound person take in a week = 55X9
=495ml
Given that total number of books in the book store = 75972
Given that total number of books in science section =
rd of total books =
= 25324
Then remaining number of books = 75972 - 25324 = 50648
Given that 75% of the remaining books are in business section = 75% of 50648 = 0.75*50648 = 37986
Then number of books in the math section = 50648 - 37986 = 12662
Hence final answer is 12662 books in the math section.