A section of road with a length of 324 meters was built, and a total of 240 meters was built in the first 8 hours. If the repair is completed in the remaining 4 hours, how much will be repaired per hour?
修一段长324米的路，前8小时共修了240米，如果剩下的4小时修完，每小时修多少？
<gadget id="calculator">324 - 240</gadget>
<output>84</output>

<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<result>21</result>