Read a book, read the whole book (1/5) on the first day, and read 60 pages on the second day. At this time, you have read exactly half of the whole book. How many pages does this book have?
读一本书，第一天读了全书的(1/5)，第二天读了60页，这时已读的正好是全书的一半，这本书共有多少页？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">60 / (3/10)</gadget>
<output>200</output>

<result>200</result>