The speed ratio of an express train to a slow train is 5:7. The two trains are traveling towards each other from Station A and Station B at the same time, and meet at a distance of 12 kilometers from the midpoint. How many kilometers are there between A and B?
一列快车和一列慢车的速度比是5：7，两车同时从甲、乙两站相向而行，在离中点12千米的地方相遇．甲、乙两站相距多少千米？
<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">(7/12) - (5/12)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">2 / (1/6)</gadget>
<output>12</output>

<gadget id="calculator">12 * 12</gadget>
<output>144</output>

<result>144</result>