The distance between A and B is 312 kilometers. A bus and a truck drive toward each other at the same time. They meet each other in 4 hours. The bus travels 30 kilometers per hour. How many kilometers per hour does the truck travel?
甲乙两地相距312千米，一辆客车和一辆货车同时从两地相向而行，4小时相遇，客车每小时行30千米，货车每小时行多少千米？
<gadget id="calculator">312 / 4</gadget>
<output>78</output>

<gadget id="calculator">78 - 30</gadget>
<output>48</output>

<result>48</result>