1 gallon of milk costs 0.50 more than 5 times a gallon of water.
From that information milk is 5x +0.50 the cost of water.
The cost of milk is $3.75, so now we have:
3.75 = 5x + 0.50
Subtract 0.50 from each side:
3.25 = 5x
Divide both sides by 5:
X = 3.25 / 5
x = 0.65
The cost of water = $0.65