You can walk this distance in 20 minutes, and after walking for 15 minutes, there is still ((())/(())) left for this distance.
20分钟可以走完这段路，走了15分钟，还剩这段路的((())/(()))．
<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

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

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