The ratio of the speed of the truck to the speed of the passenger car is 3:4. The two cars are driving opposite each other from Station A and B at the same time, and meet at a distance of 6 kilometers from the midpoint. When the bus arrives at Station A, how far is the truck from Station B?
货车速度与客车速度比是3：4，两车同时从甲乙两站相对行驶，在离中点6千米处相遇，当客车到达甲站时，货车离乙站还有多远？
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

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

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

<gadget id="calculator">(4/7) - (3/7)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">12 / (1/7)</gadget>
<output>84</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">84 * (1/4)</gadget>
<output>21</output>

<result>21</result>