Given the task definition, example input & output, solve the new input case.
You are given a math word problem and you are supposed to apply multiple mathematical operators like addition, subtraction, multiplication, or division on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
Example: for a birthday party cody bought 30 regular sodas and 5 diet sodas . if his fridge would only hold 7 on each shelf how many shelves would he fill up ?
Output: 5
total sods = 30+5 = 35, total shelves filled = total soda/7 = 35/7 = 5

New input case for you: roger is at the library helping put away books . there are 54 book to put away total but a librarian takes 19 of them and leaves roger with the rest . if he can fit 5 books on a shelf how many shelves will he need ?
Output:
7