Xiao Ming reads a storybook. He reads 30% of the book on the first day, and (1/5) of the book on the second day. At this time, there are still 20 pages left. How many are there in this storybook? Page?
小明看一本故事书，第一天看了这本书的30%，第二天看了这本书的(1/5)，这时还剩20页没有看，这本故事书一共有多少页？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (3/10) - (1/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / (1/2)</gadget>
<output>40</output>

<result>40</result>