To build a section of road 324 meters long, 240 meters have been built in 8 hours, and the rest will be completed in 4 hours. How many meters will be repaired per hour on average?
修一段长324米的路，8小时已修了240米，剩下的要4小时完成，剩下的平均每小时要修多少米才能修完？
<gadget id="calculator">324 - 240</gadget>
<output>84</output>

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

<result>21</result>