Cars A and B start from the same place at the same time and drive toward each other. After 3.6 hours, the distance is 306 kilometers. The speed of car A is 42 km/h, find the speed of car B.
甲、乙两辆汽车同时从同一地点出发，相背而行，3.6小时候后相距306千米．甲车的速度是每小时42千米∕时，求乙车的速度．
<gadget id="calculator">306 / 3.6</gadget>
<output>85</output>

<gadget id="calculator">85 - 42</gadget>
<output>43</output>

<result>43</result>