TASK DEFINITION: The task is to generate the correct answer for a given math problem.
PROBLEM: Problem: a particular library has 75 books in a special collection , all of which were in the library at the beginning of the month . these book are occasionally loaned out through an inter - library program . if , by the end of the month , 80 percent of books that were loaned out are returned and there are 66 books in the special collection at that time , how many books of the special collection were loaned out during that month ?

SOLUTION: 45

PROBLEM: Problem: a cistern is normally filled in 6 hours but takes two hours longer to fill because of a leak in its bottom . if the cistern is full , the leak will empty it in ?

SOLUTION: 24

PROBLEM: Problem: by selling an article for $ 225 a person gains $ 75 . what is the gain % ?

SOLUTION:
50 %