It takes 7 hours for a local train to travel from station A to station B, and 6 hours for an express train to travel from station B to station A. The two trains are going towards each other. The slow train leaves station A for 1 hour before the express train departs from station B. How many hours does it take to meet the slow train?
一列慢车从甲站到乙站要7小时，一列快车从乙站到甲站要6小时，两车相向而行，慢车从甲站先开出1小时后，快车才由乙站开出，快车开出几小时后才能和慢车相遇？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

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

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/7) + (1/6)</gadget>
<output>13/42 = around 0.309524</output>

<gadget id="calculator">(6/7) / (13/42)</gadget>
<output>36/13 = around 2.769231</output>

<result>36/13 = around 2.769231</result>