car travels from A to B at a speed of 84 km/h and arrives in 6 hours. When I came back, it was raining and it took 9 hours. What was the average speed of the car in km/h when it returned?
一辆汽车以84千米/时的速度从甲地开往乙地，6小时到达．回来时遇到下雨，用了9小时．这辆汽车返回时的平均速度是多少千米/时？
<gadget id="calculator">6 / 9</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">84 * (2/3)</gadget>
<output>56</output>

<result>56</result>