Two ships are sailing relative to each other from two ports at the same time. Ship A travels 28 kilometers per hour, and ship B travels 35 kilometers per hour. After 12 hours, the distance between the two ports is still 30 kilometers. What is the distance between the two ports in kilometers?
两艘轮船同时从两个港口相对航行，甲轮船每小时航行28千米，乙轮船每小时航行35千米，经过12小时还相距30千米，两个港口之间的航程是多少千米．
<gadget id="calculator">28 * 12</gadget>
<output>336</output>

<gadget id="calculator">35 * 12</gadget>
<output>420</output>

<gadget id="calculator">336 + 420 + 30</gadget>
<output>786</output>

<result>786</result>