An express train and a slow train depart from A and B respectively at the same time. After meeting each other for 12 hours, the express train travels for another 8 hours to reach B. How many hours will it take for the slow train to reach A after the encounter?
一辆快车和一辆慢车同时分别从甲、乙两地相对开出，经12小时相遇后，快车又行了8小时到达乙地，那么相遇后慢车还要行多少小时才能到达甲地．
<gadget id="calculator">12 / 8</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">1 / (3/2)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">12 / (2/3)</gadget>
<output>18</output>

<result>18</result>