after a heavy rain a river is 18 inches above its normal water level, the water level will drop about 3 inches every hour about how much time will it take for the water level to return to normal.

6 Hours

Explanation: If it raised 18 inches above its regular water level, and its drops 3 inches every hour, Just think like ok
Hour 1: 18-3=15
Hour 2: 15-3= 12
Hour 3: 12-3= 9
Hour 4: 9-3 = 6
Hour 5: 6-3 = 3
Hour 6: 3-3= 0
Or just divide 18/3 but that’s like the full explanation haha. Hope this helps