Xiaolan reads a story book. She reads 30% of it on the first day, and reads 12 pages less on the second day than on the first day. At this time, she still has half of it. How many pages does this book have?
小兰看一本故事书，第一天看了它的30%，第二天比第一天少看了12页，这时还有一半没有看，这本书共有多少页？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/10) - (1/5)</gadget>
<output>1/10 = around 0.1</output>

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

<result>120</result>