Xiaodong reads a storybook. He read 20% of the whole book on the first day, 24 pages on the second day, and half of the book in two days. How many pages does this storybook have?
小东看一本故事书，第一天看了全书的20%，第二天看了24页，两天正好看了全书的一半，这本故事书有多少页？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">24 / (3/10)</gadget>
<output>80</output>

<result>80</result>