An express train and a slow train depart from A and B at the same time, and they meet after 3 hours. The distance between the meeting point and the midpoint of A and B accounts for 1/7 of the whole journey. It is known that the express train is more than the slow train per hour. Line 60 kilometers. What is the distance in miles between A and B?
一列快车和一列慢车从甲、乙两地同时相对开出，3小时后相遇，相遇点距甲、乙两地中点的距离占全程的(1/7)，已知快车比慢车每小时多行60千米．甲、乙两地之间的距离是多少千米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/2) + (1/7)</gadget>
<output>9/14 = around 0.642857</output>

<gadget id="calculator">(1/2) - (1/7)</gadget>
<output>5/14 = around 0.357143</output>

<gadget id="calculator">(9/14) - (5/14)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">3 / (2/7)</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">60 * (21/2)</gadget>
<output>630</output>

<result>630</result>