We have four containers. The first three contain water, the fourth is empty. In the second one, there is twice as much water as in the first, and in the third one, there is twice as much water as in the second. We pour half of the water from the first container, a third of the water from the second container, and a quarter of the water from the third container into the fourth container. Now, the fourth container has 26 liters of water. How much water is there in total in all the containers?

(M. Raabová)
From the text, it follows that in the first container there is one part of water, in the second container there are two parts of water, and in the third container there are four parts of water. To make it easier to remove water from each container, we will divide each part into six sixths. So, in the first container there are 6 pieces, in the second 12, and in the third 24 pieces of water. Now we pour into the fourth container 3 pieces from the first, 4 pieces from the second, and 6 pieces from the third container. This is a total of 13 pieces, which is 26 liters. Therefore, one piece is two liters of water.

Originally, there were: 12 liters in the first container, 24 liters in the second container, and 48 liters in the third container, i.e., a total of 84 liters of water.