Answer: At least one of the textbooks is free of errors.
In statistics, the complement rule allows us to connect the probability of an event with the probability of the complement of an event. This is done so that, if we know the probability of one of these two, we can find out that of the other. In this case, the complement of the given event (when several textbooks are edited, none of them are found to be free of errors) is: At least one of the textbooks is free of errors.