story book has 100 pages. I read (1/2) of the whole book on the first day, and 20 pages on the second day, leaving ((())/(())) unread.
一本故事书有100页，第一天看了全书的(1/2)，第二天看了20页，还剩((())/(()))没看．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">100 * (1/2)</gadget>
<output>50</output>

<gadget id="calculator">50 + 20</gadget>
<output>70</output>

<gadget id="calculator">100 - 70</gadget>
<output>30</output>

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

<result>3/10 = around 0.3</result>