Sara is looking for a book in the library. The librarian tells her, "all the shelves in our library are arranged in one row. The book you are looking for is located on the $$8$$\textsuperscript{th} shelf if you count from front to back, and the $$10$$\textsuperscript{th} if you count from back to front. " How many shelves are there in the library? 
Overseas Competition->Knowledge Point->Word Problem Modules->Problems Involving Queuing->Finding the Total Number According to the Position of one Character in a Line