A and B are 15 kilometers apart. They are walking in the same direction at the same time. B is in front and travels 4 kilometers per hour. A is behind and travels 6 kilometers per hour. After how many hours, A will pass B by 2 kilometers.
甲、乙两人相距15千米，两人同时同向而行，乙在前，每小时行4千米，甲在后，每小时行6千米，经过多少小时甲超过乙2千米．
<gadget id="calculator">15 + 2</gadget>
<output>17</output>

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

<gadget id="calculator">17 / 2</gadget>
<output>17/2 = around 8.5</output>

<result>17/2 = around 8.5</result>