Three engineering teams, A, B, and C, jointly build a 21-kilometer road. Team A repairs (1/3) of the full length, Team B repairs the full length (3/7), and the rest is completed by Team C. ． What percentage of this road has Team C repaired?
甲、乙、丙三个工程队合修一条21千米长的公路，甲队修了全长的(1/3)，乙队修了全长的(3/7)，其余的由丙队修完．丙队修了这条公路的几分之几？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (1/3) - (3/7)</gadget>
<output>5/21 = around 0.238095</output>

<result>5/21 = around 0.238095</result>