A cargo ship sails from A to B with a speed of 35 km/h. It takes 12 hours to reach B and returns with a speed of 42 km/h. How long will it take to return to A? ?
一艘货船从甲地开往乙地，去时速度是35千米/小时，用了12小时到达乙地，返回时速度是42千米/小时，返回时要用多长时间回到甲地？
<gadget id="calculator">12 / 42</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">35 * (2/7)</gadget>
<output>10</output>

<result>10</result>