It takes 6 hours for ship A to travel from the east port to the west port, and it takes 4 hours for ship B to travel from the west port to the east port. Now the two ships set off from the east and west ports at the same time and head towards each other, and finally meet at a distance of 18 kilometers from the midpoint. How many kilometers did A travel when they met?
甲船从东港到西港要行6小时，乙船从西港到东港要行4小时．现在两船同时从东西两港出发，相向而行，结果在离中点18千米处相遇．相遇时甲行了多少千米？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / (1/5)</gadget>
<output>10</output>

<gadget id="calculator">18 * 10 * (2/5)</gadget>
<output>72</output>

<result>72</result>