On a straight road, Ke Ke and Fan Fan start at the same time from a distance of 100 meters, and run towards each other. Afterwards, the direction remains unchanged. Ke Ke runs 6 meters per second, and Fan Fan runs 4 meters per second. How many seconds before starting, they were 200 meters apart.
在一条笔直的公路上，可可和凡凡从相距100米的地方同时出发，相向跑步，以后方向都不变，可可每秒跑6米，凡凡每秒跑4米．出发多少秒时，他们相距200米．
<gadget id="calculator">100 + 200</gadget>
<output>300</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">300 / 10</gadget>
<output>30</output>

<result>30</result>