A book has 80 pages, I read (3/4) of the whole book on the first day, how many pages are left.
一本书有80页，第一天看了全书的(3/4)，还有多少页没看．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 * (1/4)</gadget>
<output>20</output>

<result>20</result>