From a log 5 meters long we sawed off a part 20 decimetres long to find out the length of the remaining part of the log.

This task is simple, therefore, in order to solve it and get the correct answer, you will need to perform only one action.
But first, we need to draw up a short condition for this task:
Initial length – 5 meters;
Cut off – 20 decimeters;
Left – ? meters;
First, let’s convert decimeters to meters, since the values must be the same:
20 decimeters = 2 meters;
Now we will find the length of the remaining part of the log. To do this, subtract the length of the cut part from the initial length of the log:
5 – 2 = 3 meters;
Answer: 3 meters