A car has traveled the entire distance (3/7) from point A to point B, and it is 40 kilometers away from the midpoint. How many kilometers has it traveled?
一辆汽车从甲地开往乙地，已经行了全程的(3/7)，离中点还有40千米，已行了多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</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">40 / (1/14)</gadget>
<output>560</output>

<gadget id="calculator">560 * (3/7)</gadget>
<output>240</output>

<result>240</result>