Answer: 4 hours
Explanation:
The water level changes at an average rate of 3 meters per hour.
The question wants to know how long it will take for the ocean water level to change 12 meters.
You can use direct proportion:
1 hour : 3 meters
x hours : 12 meters
Cross multiply to get:
3x = 12
x = 12 / 3
= 4 hours