Two trains depart from two stations A and B in opposite directions at the same time. They meet for the first time at a place 40 kilometers away from station A. After the two trains meet, they still move forward at the same speed. , how many kilometers are there between the two stations A and B?
两列火车同时从甲乙两站相向开出，第一次相遇离甲站40公里的地方，两车相遇后仍以原速度前进，分别站后立即返回，又在离乙站20公里的地方相遇，求甲乙两站相距多少公里？
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">120 - 20</gadget>
<output>100</output>

<result>100</result>