The article contains a strict description of a situation in which the conditional probability of one event relative to another can be calculated as the probability of the first, provided that the second occurred. This gives a theoretical justification for the solutions of probabilistic problems using the concept of conditional probability.
Annotation: the article on a number of examples of equations with separable variables showed that the search for a general solution with strict adherence to the definitions may be associated with unjustified difficulties, whereas the description of the set of solutions in an arbitrary form is quite simple.
