Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.
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Question: roger mowed his lawn 15 times total during the spring and summer . if he mowed it 9 times in the summer . how many times did he mow in the spring ?

Answer: 6

Question: after visiting france rachel 's sister bella requested that they see the buckingham palace in london . if they travelled 451 miles by land and 150 miles by sea across the english channel what is the total distance that they travelled ?

Answer: 601

Question: victor had 9 books . during the book fair he bought 3 more . how many books did victor have total ?

Answer:
12