Wang Gang and Li Ming were running on the 600-meter circular playground. The two set off at the same time and walked in opposite directions. Wang Gang runs 7 meters per second, and Li Ming runs 8 meters per second. How many seconds later did the two meet?
王刚与李明在600米的环形操场上跑步．两人同时出发，反向而行．王刚每秒跑7米，李明每秒跑8米．多少秒后两人相遇？
<gadget id="calculator">7 + 8</gadget>
<output>15</output>

<gadget id="calculator">600 / 15</gadget>
<output>40</output>

<result>40</result>