Zhou Liang read a story book, read 20% of the whole book on the first day, and 30% of the whole book on the second day, leaving 60 pages unread. How many pages are there in this book?
周亮看一本故事书，第一天看了全书的20%，第二天看了全书的30%，还剩60页没有看．这本书一共多少页？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

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

<gadget id="calculator">60 / (1/2)</gadget>
<output>120</output>

<result>120</result>