For the sake of simplicity, let us say that the bottle contains x liters of water.
The pail originally contained x+3.68 L of water
After pouring out 1.2L, the pail contains x+(3.68-1.2)L or x+2.48 L
(a) How much more water did the pail contain than the bottle in the end?
Since the bottle contains x L of water, the pail (containing x+2.48 L of water) contains (x+2.48) - x more liters of water than the bottle or "the pail contained 2.48 L of water more than the bottle"
(b) How much water did the bottle contain?
We are told that after pouring the 1.2L of water out, the pail contained 3 times as much water as the pail. Therefore, 3x = x+2.48. Subtracting x from both sides gives us 2x = 2.48. Dividing both sides by 2 gives us x = 1.24L
