A and B are 13 kilometers apart and they are walking in the same direction at the same time. B is in front and travels 4 kilometers per hour, and A and B are behind and travels 6 kilometers per hour. After how many hours, A surpasses B by 3 kilometers.
甲乙两人相距13千米，两人同时同向行走．乙在前，每小时行4千米，甲乙在后，每小时行6千米．经过多少小时甲超过乙3千米．
<gadget id="calculator">13 + 3</gadget>
<output>16</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>