There were 78 liters of water in two containers. When 12 liters of water were taken from one container, the water in both containers became equal. How many liters of water were in each container at the beginning?

Let's call the amount of water in the first container X liters, and the amount of water in the second container Y liters. According to the given information, the total amount of water in both containers at the beginning is 78 liters. So, we have the equation: X + Y = 78 When 12 liters of water were taken from the first container, the amount of water in the first container becomes X - 12, and the amount of water in the second container remains Y. In this case, the water in both containers becomes equal. Therefore, we have the equation: X - 12 = Y Now, we can substitute the second equation into the first equation: X + (X - 12) = 78 2X - 12 = 78 2X = 90 X = 45 Substitute X back into the second equation to find Y: 45 - 12 = Y Y = 33 Therefore, at the beginning, there were 45 liters of water in the first container and 33 liters of water in the second container.