The passenger car and the freight car departed from two stations 840 kilometers apart at the same time, and met on the way in 6 hours. It is known that the passenger car travels 80 kilometers per hour, how many kilometers per hour does the truck travel?
客车和货车分别从相距840千米的两站同时相对开出，6小时在途中相遇．已知客车每小时行80千米，货车每小时行多少千米？
<gadget id="calculator">840 / 6</gadget>
<output>140</output>

<gadget id="calculator">140 - 80</gadget>
<output>60</output>

<result>60</result>