Problem 1. In the bookstore, 8450 notebooks were delivered. On the first day, half of them were sold, and on the second day, 437 fewer notebooks were sold. How many notebooks remained unsold?
Solution. On the first day, $8450: 2=4225$ notebooks were sold, and on the second day $4225-437=3788$ notebooks were sold. Not sold remained

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8450-(4225+3788)=437
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notebooks.