The speed of the bus is (4/7) of the speed of the car. Now the two cars are traveling toward each other from two places at the same time, and meet at a distance of 15 kilometers from the midpoint. How many kilometers did the car travel when they met?
大客车的速度是小轿车速度的(4/7)．现在两车同时从两地相向而行，在离中点15千米处相遇，相遇时小轿车行驶了多少千米？
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">30 / (3/7)</gadget>
<output>70</output>

<result>70</result>