A and B are traveling towards each other along the railway line at the same speed. It takes 7 seconds for a train to pass by A, 4 minutes later the train meets B, and it takes 5 seconds to pass by B, then how many minutes after the train meets B, how many minutes will A and B meet?
甲、乙两人沿铁路线相向而行，速度相同．一列火车从甲身边开过用了7秒，4分后火车与乙相遇，且从乙身边开过用了5秒，那么从火车遇到乙开始，再过多少分甲、乙两人相遇？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) + (1/7)</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">(12/35) / 2</gadget>
<output>6/35 = around 0.171429</output>

<gadget id="calculator">(1/5) - (1/7)</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">(2/35) / 2</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(6/35) / (1/35)</gadget>
<output>6</output>

<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>