Xiaohong reads an extra-curricular book. She reads (3/8) of the whole book on the first day, and the rest (2/5) on the second day. There are still 300 pages left. How many pages does this book have?
小红看一本课外书，第一天看了全书的(3/8)，第二天看了余下的(2/5)，还剩下300页．这本书有多少页？
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (3/8)</gadget>
<output>5/8 = around 0.625</output>

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

<gadget id="calculator">(5/8) * (2/5)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (3/8) - (1/4)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">300 / (3/8)</gadget>
<output>800</output>

<result>800</result>