Two people, A and B, start from A and B at the same time and walk toward each other. A travels 6 kilometers per hour, and B travels 4 kilometers per hour. They meet at a place 3 kilometers away from the midpoint of A and B. Find the distance between A and B.
甲、乙两人分别从A、B两地同时出发相向而行，甲每小时6千米，乙每小时行4千米，在离A、B两地中点3千米的地方相遇．求A、B两地的距离．
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">10 * 3 * 1</gadget>
<output>30</output>

<result>30</result>