A car travels from Yanling to Zhuzhou. It takes 2 hours on the expressway at a speed of 120 km/h. When returning, it takes 3 hours on an ordinary road at a speed of 75 km/h. Which route is it? If the distance is longer, how many more kilometers do you need to walk?
一辆汽车从炎陵去株洲，走高速公路的速度是120千米/小时，用了2小时，返回时走普通公路的速度是75千米/小时，用了3小时，请问哪条线路的距离更长，要多走多少千米？
<gadget id="calculator">120 * 2</gadget>
<output>240</output>

<gadget id="calculator">75 * 3</gadget>
<output>225</output>

<gadget id="calculator">240 - 225</gadget>
<output>15</output>

<result>15</result>