The distance between A and B is 450 kilometers. Two fast and slow trains leave from the two places at the same time. After 3 hours, the two trains meet at a distance of 12 kilometers from the midpoint. How many kilometers per hour is the speed of the fast train compared with the slow train?
甲乙两地相距450千米，快慢两列火车同时从两地相向开出，3小时后两车在距中点12千米处相遇，快车每小时比慢车每小时快多少千米．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">12 * (2/3)</gadget>
<output>8</output>

<result>8</result>