A book, how much has been read, the remaining 25% have not been read.
一本书，读了多少，剩下25%没有读完．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>