The ordinary road from Zhaotong to Kunming is 480 kilometers long, and the expressway is 320 kilometers long. A car travels 40 kilometers per hour on the ordinary road and 80 kilometers per hour on the expressway. This car travels faster on the expressway than on the ordinary road. How many hours are saved?
从昭通到昆明的普通公路长480千米，高速公路长320千米，一辆汽车走普通公路每小时40千米，走高速公路每小时80千米，这辆汽车走高速公路比走普通公路节省多少小时？
<gadget id="calculator">480 / 40</gadget>
<output>12</output>

<gadget id="calculator">320 / 80</gadget>
<output>4</output>

<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<result>8</result>