If you have read 9 pages of a book, the number of pages you have not read is 3 times the number of pages you have read. How many pages does this book have?
一本书看了9页，没看的是已看的3倍，这本书一共有多少页．
<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<gadget id="calculator">27 + 9</gadget>
<output>36</output>

<result>36</result>