A. Two cars start from the same place at the same time, and go opposite to each other. After 2.4 hours, the distance is 216 kilometers. The speed of car A is 42 km/h, find the speed of car B. (solution with equation)
甲、两辆汽车同时从同一地点出发，相背而行，2.4小时后相距216千米．甲车的速度是42千米/时，求乙车的速度．(用方程解答)
<gadget id="calculator">2.4 * 42</gadget>
<output>100.8</output>

<gadget id="calculator">216 - 100.8</gadget>
<output>115.2</output>

<gadget id="calculator">115.2 / 2.4</gadget>
<output>48</output>

<result>48</result>