A car drives from place A to place B. The ratio between the traveled distance and the remaining distance is 3:4. If it travels another 20 kilometers, it will be exactly half of the journey. Find the distance between A and B in thousands rice?
一辆汽车从甲地开往乙地，已行路程与剩下的路程之间的比是3：4，如果再行20千米，就正好行了全程的一半，求甲乙两地相距多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">(1/2) - (3/7)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">20 / (1/14)</gadget>
<output>280</output>

<result>280</result>