The distance between A and B is 420 kilometers. A truck and a bus depart from A and B respectively at the same time and drive toward each other. The two cars meet on the way 3 hours after departure. It is known that the passenger car travels 80 kilometers per hour, how many kilometers per hour does the truck travel? (solution by equation)
甲、乙两地相距420千米，货车和客车分别从甲、乙两地同时出发，相向而行．两车出发3小时后在途中相遇，已知客车每小时行80千米，货车每小时行多少千米？(用方程解)
<gadget id="calculator">80 * 3</gadget>
<output>240</output>

<gadget id="calculator">420 - 240</gadget>
<output>180</output>

<gadget id="calculator">180 / 3</gadget>
<output>60</output>

<result>60</result>