Read a book mischievously. On the first day, I read 30% of the whole book. On the second day, I read 30 pages less than the first day. At this time, I still haven’t read half of the book. How many pages does this book have?
淘气看一本书，第一天看了整本书的30%，第二天比第一天少看30页，这时还有一半没看，这本书共有几页？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">30 / (1/10)</gadget>
<output>300</output>

<result>300</result>