To build a road, the whole road (2/7) was built on the first day, and the whole road (1/5) was built on the second day, and the remaining part of the road was not repaired.
修一条公路，第一天修了全路的(2/7)，第二天修了全路的(1/5)，还剩全路的多少没有修．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (2/7) - (1/5)</gadget>
<output>18/35 = around 0.514286</output>

<result>18/35 = around 0.514286</result>