A section of road is 500 meters, a car starts at 7:00 in the morning, and finds out at 9:00, there are 300 meters left to the finish line, how many kilometers per hour does the car travel on average?
一段路500米，一辆车早晨7点开始出发，9点发现，离终点还剩300米，汽车平均每小时行多少千米？
<gadget id="calculator">500 - 300</gadget>
<output>200</output>

<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<gadget id="calculator">200 / 2</gadget>
<output>100</output>

<result>100</result>