A particular library has 150 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 122 books in the special collection at that time, how many books of the special collection were loaned out during that month?  Choose the correct choice from the following answers.
A) 40 B) 60 C) 80 D) 100 E) 120
The total number of books is 150.   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 122 books, thus the number of un-returned books is 150-122= 
<gadget id="calculator">150-122</gadget>
<output>28</output>
28 books.   0.35x= 28   x = 80   The answer is 80.
<result>C</result>
A particular library has 150 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 122 books in the special collection at that time, how many books of the special collection were loaned out during that month?