A and B are running along a 400-meter circular track. They start from the same place at the same time and walk in the same direction. A runs 280 meters per minute, and B runs 240 meters per minute. After how many minutes does A run two more laps than B? (solution with equation)
甲、乙两人沿着400米的环形跑道跑步，他们同时从同一地点出发，同向而行．甲每分钟跑280米，乙每分钟跑240米．经过多少分甲比乙多跑两圈？(用方程解答)
<gadget id="calculator">400 * 2</gadget>
<output>800</output>

<gadget id="calculator">280 - 240</gadget>
<output>40</output>

<gadget id="calculator">800 / 40</gadget>
<output>20</output>

<result>20</result>