Xiaohong reads a book. She reads 30% of the whole book on the first day, and 20% of the whole book on the second day. At this time, there are still 36 pages left. How many pages does this book have?
小红看一本书，第一天看了全书的30%，第二天看了全书的20%，这时还剩下36页没有看．这本书一共有多少页？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 / 100</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">36 / (1/2)</gadget>
<output>72</output>

<result>72</result>