A train is 75 meters long, travels 24 meters per second, and passes through a tunnel in 30 seconds. How long is the tunnel?
一列火车长75米，每秒行驶24米，30秒通过一条隧道，这条隧道长多少米？
<gadget id="calculator">24 * 30</gadget>
<output>720</output>

<gadget id="calculator">720 - 75</gadget>
<output>645</output>

<result>645</result>