You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
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Question: A carpenter bought a piece of wood that was 0.41 meters long . Then she sawed 0.33 meters off the end . How long is the piece of wood now ?

Answer: 0.08

Question: Sara grew 4 onions , Sally grew 5 onions , and Fred grew 9 onions . How many onions did they grow in all ?

Answer: 18

Question: Rachel was organizing her book case making sure each of the shelves had exactly 9 books on it . If she had 6 shelves of mystery books and 2 shelves of picture books , how many books did she have total ?

Answer:
72