Li Tong reads a 60-page story book. He reads (1/4) of this book on the first day and (1/2) of this book on the second day. How much of this book is left? look.
李童看一本60页的故事书，他第一天看了这本书的(1/4)，第二天看了这本书的(1/2)，还剩这本书的多少没有看．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">1 - (1/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>