A walks, and B rides a bicycle. They start from A and B at the same time and walk toward each other. After meeting, A continues to walk to B, and B immediately returns to B. As a result, B arrives at B two hours earlier than A. It is known that A's speed is B's (3/7), how many hours does it take B to ride a bicycle from B to A?
甲步行，乙骑自行车，分别从A、B同时出发，相向而行，相遇后甲继续向B地走，乙马上返回也向B地行，结果乙比甲早两个小时到达B地．已知甲速是乙速的(3/7)，问从B地到A地，乙骑自行车需要多少小时？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">(1/2) * 10</gadget>
<output>5</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">5 * (3/7)</gadget>
<output>15/7 = around 2.142857</output>

<result>15/7 = around 2.142857</result>