In a book, the ratio of the number of pages you have read to the number of pages you have not read is 3:7, and the number of pages you have read is 18 pages less than the number of pages you have not read. How many pages are there in the book?
一本书，已看的页数与为看的页数的比是3：7，已看的页数比未看的页数少18页，全书有多少页？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">18 / 4</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">(9/2) * 10</gadget>
<output>45</output>

<result>45</result>