In the study of RVs, questions of the following form arise. What is the probability that the RV x is less than a giver number X, or what is the probability that x is between the numbers x1 and x2. If, for example, the RV is the height of a person, we might want the probability that it will not exceed certain bounds. As we know, probabilities are assigned only to events. Therefore, in order to answer such questions we should be able to express the various conditions imposed on x as events.

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