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, 65 percent of books that were loaned out are returned and there are 54 books in the special collection at that time, how many books of the special collection were loaned out during that month?  Choices:
A) 20
B) 30
C) 35
D) 40
E) 60
The total number of books is 75.   Let x be the number of books which were loaned out.   65% of books that were loaned out are returned.   35% of books that were loaned out are NOT returned.   Now, there are 54 books, thus the number of un-returned books is 75-54= 
<gadget id="calculator">75-54</gadget>
<output>21</output>
21 books.   0.35x= 21   x = 60   The answer is 60.
<result>E</result>
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, 65 percent of books that were loaned out are returned and there are 54 books in the special collection at that time, how many books of the special collection were loaned out during that month?