The speed of train A is 60 km/h and the speed of train B is 68 km/h. At 7 o'clock in the morning, train A departs from Chongqing to Chengdu; at 9 o'clock in the morning, train B departs from Chengdu to Chongqing, and at 12 o'clock, the two trains meet. How many kilometers is the distance between Chongqing and Chengdu?
甲列车的速度为60千米每小时，乙列车的速度为68千米每小时．上午7时，甲列车从重庆开往成都；上午9时，乙列车从成都开往重庆，12时，两列车相遇．重庆与成都两站相距多少千米？
<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<gadget id="calculator">60 * 5</gadget>
<output>300</output>

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<gadget id="calculator">68 * 3</gadget>
<output>204</output>

<gadget id="calculator">300 + 204</gadget>
<output>504</output>

<result>504</result>