In this big ol' word problem, this is just an instance of basic multiplication/division.
If it takes it 1 hour for 3 meters...
12 ÷ 3 = 4.
It would take 4 hours for the water level to change to 12 meters.
X=(b/2m)*y-e is the answer I believe.
The slope can be calculated with the following formula:
![m=\frac{y_2-y_1}{x_2-x_1}](https://tex.z-dn.net/?f=m%3D%5Cfrac%7By_2-y_1%7D%7Bx_2-x_1%7D)
In this case, you have the following points: