A book, after reading for a week (with the same number of pages per day), there are still 9% of the book left, if you read less (3/13) every day, then there will be 210 pages left after reading for a week. How many pages does this book have.
一本书，看了一周后(每天看的页数相同)还剩全书的9%没看，如果每天少看(3/13)，那么看一周后将还剩210页．这本书原有多少页．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">210 / (7/10)</gadget>
<output>300</output>

<result>300</result>