The speed ratio of A and B is 7:5. If A and B travel towards each other along the same route from A and B respectively, it will take 4 hours for A to catch up with B. How many hours will they meet if they travel in the same direction?
甲、乙两人的速度的比是7：5，如果甲乙分别从A、B两地沿同一线路相向而行，甲追上乙需要4小时，如果相向而行多少小时相遇．
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">4 / 12</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">2 * (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>