The road between A and B is 265 kilometers long. The passenger car drives from A to B at a speed of 42 kilometers per hour. At the same time, the truck drives from B to A. After traveling for 3 hours, the two cars are still 4 kilometers apart. ． How many miles does the truck travel per hour?
甲乙两站的公路长265千米，客车以每小时42千米的速度从甲站开往乙站，同时货车从乙站向甲站开出，行了3小时，两车还相距4千米．货车每小时行多少千米？
<gadget id="calculator">265 - 4</gadget>
<output>261</output>

<gadget id="calculator">261 / 3</gadget>
<output>87</output>

<gadget id="calculator">87 - 42</gadget>
<output>45</output>

<result>45</result>