The road between A and B is 420 kilometers long. A car drives from place A to place B. After driving for 4 hours, it is still 120 kilometers away from place B. How many kilometers per hour does the car travel on average? (column equation solution)
甲乙两地之间的公路长420千米．一辆汽车从甲地开往乙地，行驶了4小时离乙地还有120千米．这辆汽车平均每小时行驶多少千米？(列方程解答)
<gadget id="calculator">420 - 120</gadget>
<output>300</output>

<gadget id="calculator">300 / 4</gadget>
<output>75</output>

<result>75</result>