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: the library has 75 science books . the second graders borrowed 18 of them . how many science books are left ?

Answer: 57

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: victor had 19 apps on his phone . he deleted 8 of them . how many apps does victor have left ?

Answer:
11