Count one book, read 30% of the whole book on the first day, read 20 pages on the second day, and left (3/5) of the whole book unread, how many pages does this book have in total?
一本数，第一天看了全书的30%，第二天看了20页，还剩全书的(3/5)没有看，这本书一共有多少页？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/10) - (3/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / (1/10)</gadget>
<output>200</output>

<result>200</result>