The distance from Nanjing to Shanghai is 280 kilometers. A car will be 20 kilometers away from Shanghai after 4 hours from Nanjing. How many kilometers does this car travel on average per hour?
南京到上海有280千米，一辆汽车从南京出发4小时后离上海还有20千米，这辆汽车平均每小时行多少千米？
<gadget id="calculator">280 - 20</gadget>
<output>260</output>

<gadget id="calculator">260 / 4</gadget>
<output>65</output>

<result>65</result>