15.6.9 Definition and properties of probability

Problem: The auditor checks three accounts. The probability of correct registration of the account is equal to 0,9 . Find the probability of the events: \( A=\{3 \) accounts are correctly registered \( \} \), \( B=\{2 \) accounts are correctly registered \( \} \), \( C=\{1 \) account is correctly registered \( \} \), \( D=\{ \) at least 1 account is correctly registered \( \} \).