Xiaohua reads a book and reads 20 pages a day. After 6 days, 40% of the book remains. How many pages does this book have?
小华看一本书，每天看20页，6天后还剩全书的40%，这本书有多少页？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">6 / (3/5)</gadget>
<output>10</output>

<gadget id="calculator">20 * 10</gadget>
<output>200</output>

<result>200</result>