A road has been repaired (2/7), the repaired road is less than the unrepaired road by how much
一条公路，已修(2/7)，已修的比未修的少这条公路的多少
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) - (2/7)</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>