To build a road, the full length (3/7) will be built on the first day, the full length (2/5) will be built on the second day, and the rest will be finished on the third day. What fraction of the total length was repaired on the third day?
修一条路，第一天修了全长的(3/7)，第二天修了全长的(2/5)，第三天要把剩下的修完．第三天修了全长的几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/7) + (2/5)</gadget>
<output>29/35 = around 0.828571</output>

<gadget id="calculator">1 - (29/35)</gadget>
<output>6/35 = around 0.171429</output>

<result>6/35 = around 0.171429</result>