The express train and the slow train travel towards each other from AB at the same time, and after 12 hours they meet, the express train arrives at B after 6 hours, and how many hours later can the slow train reach A?
快车和慢车同时从AB两地相向而行，经过12小时相遇，6小时后快车到达B地，几个小时后慢车可以到达A地？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/12) - (1/18)</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">1 / (1/36)</gadget>
<output>36</output>

<gadget id="calculator">36 - 12</gadget>
<output>24</output>

<result>24</result>