The distance between two cities A and B is 420 kilometers. A car has traveled the entire distance (5/7) from city A to city B. How many kilometers will it take to reach city B?
A、B两城市间相距420千米，一辆汽车从A城开往B城，已行驶了全程的(5/7)，此时还要行驶多少千米才到达B城？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">420 * (2/7)</gadget>
<output>120</output>

<result>120</result>