Two cars are running backwards at the same time. After 4.5 hours, the distance between the two cars is 540 kilometers. Car A travels 52 kilometers per hour. How many kilometers per hour does car B travel?
两辆汽车同时向背而行，4.5小时后两车相距540千米，甲车每小时行52千米，乙车每小时行多少千米？
<gadget id="calculator">540 / 4.5</gadget>
<output>120</output>

<gadget id="calculator">120 - 52</gadget>
<output>68</output>

<result>68</result>