Clever question: Liangliang reads a book, reads the whole book (1/4) on the first day, and reads the rest (2/5) on the second day, and reads 15 pages less on the first day than on the second day. How many pages does this book have?
聪明题：亮亮看一本书，第一天看全书的(1/4)，第二天看余下的(2/5)，第一天比第二天少看15页．这本书共有多少页？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/4) * (2/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/10) - (1/4)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">15 / (1/20)</gadget>
<output>300</output>

<result>300</result>