Xiao Ming reads a book. He reads (1/4) of the whole book in the first week, and (1/5) of the whole book in the second week. He reads 50 pages more in the first week than in the second week. How many pages does this book have? ?
小明看一本书，第一周看了全书的(1/4)，第二周看了全书的(1/5)，第一周比二周多看了50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 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">50 / (1/20)</gadget>
<output>1_000</output>

<result>1_000</result>