The ratio of the walking speeds of A and B is 7:5. A and B start from A and B at the same time respectively. If they are walking towards each other, they will meet after 0.5 hours; if they are walking in the same direction, then A will catch up with B. How many hours will it take.
甲、乙两人步行的速度之比是7：5，甲、乙分别由A、B两地同时出发，如果相向而行，0.5小时后相遇；如果他们同向而行，那么甲追上乙需要多少小时．
<gadget id="calculator">7 * 0.5</gadget>
<output>3.5</output>

<gadget id="calculator">5 * 0.5</gadget>
<output>2.5</output>

<gadget id="calculator">3.5 + 2.5</gadget>
<output>6</output>

<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<result>3</result>