It takes 15 seconds for a train to pass through a 300-meter-long tunnel, and 12 seconds to pass through a 180-meter-long bridge. What is the length of the train body in meters?
列车通过300米长的隧道用15秒，通过180米长的桥梁用12秒，列车的车身长是多少米．
<gadget id="calculator">300 - 180</gadget>
<output>120</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">120 / 3</gadget>
<output>40</output>

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

<gadget id="calculator">600 - 300</gadget>
<output>300</output>

<result>300</result>