Two people A and B start from A and B at the same time and walk towards each other. A travels 70 meters per minute and B travels 50 meters per minute. After starting for a while, the two met at a distance of 100 meters from the midpoint. If A stops at a certain place on the way after starting, the two will meet at a distance of 250 meters from the midpoint. So how many minutes did A stay on the way?
甲、乙两人从A、B两地同时出发相向而行，甲每分钟行70米，乙每分钟行50米．出发一段时间后，两人在距中点100米处相遇．如果甲出发后在途中某地停留了一会儿，两人还将在距中点250米处相遇．那么甲在途中停留了多少分钟．
<gadget id="calculator">70 - 50</gadget>
<output>20</output>

<gadget id="calculator">2 / 20</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">70 + 50</gadget>
<output>120</output>

<gadget id="calculator">100 * (1/10) * 120</gadget>
<output>1_200</output>

<gadget id="calculator">1_200 / 2</gadget>
<output>600</output>

<gadget id="calculator">600 + 250</gadget>
<output>850</output>

<gadget id="calculator">850 / 50</gadget>
<output>17</output>

<gadget id="calculator">1_200 - 850</gadget>
<output>350</output>

<gadget id="calculator">350 / 70</gadget>
<output>5</output>

<gadget id="calculator">17 - 5</gadget>
<output>12</output>

<result>12</result>