It took a train 25 seconds to pass through a 250-meter-long tunnel; it took 23 seconds to pass through a 210-meter-long tunnel. How many seconds does it take for the train to pass by another train that is 320 meters long and travels 18 meters per second on two parallel tracks?
某列火车通过250米长的隧道用了25秒；通过210米长的隧道用了23秒．该列车与另一列长320米，每秒行驶18米的列车在两条平行轨道上相对开过需要多少秒？
<gadget id="calculator">250 + 320</gadget>
<output>570</output>

<gadget id="calculator">250 - 210</gadget>
<output>40</output>

<gadget id="calculator">25 - 23</gadget>
<output>2</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">18 + 20</gadget>
<output>38</output>

<gadget id="calculator">570 / 38</gadget>
<output>15</output>

<result>15</result>