Xiaohua reads a book and reads 20% of it on the first day. On the first day, he reads 12 pages less than on the second day. At this time, he still has half of the pages. How many pages does this book have?
小华看一本书，第一天看了20%，第一天比第二天少看12页，这时还有一半没有看，这本书有几页？
<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) - (1/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">12 / (1/10)</gadget>
<output>120</output>

<result>120</result>