Chen Ming reads a book. He reads 20% of the book on the first day and 30% of the book on the second day. He reads 15 more pages on the second day than on the first day. How many pages does the book have in total? ?
陈明读一本书，第一天读了这本书的20%，第二天读了这本书的30%，第二天比第一天多读15页，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">20 / 100</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">15 / (1/10)</gadget>
<output>150</output>

<result>150</result>