Answer: 0.31
Step-by-step explanation:
Let A denotes the event that the students report drinking alcohol and B denotes the students report using some type of tobacco product .
Given : P(A) =0.84 ; P(B)=0.33 and P(A∪B)=0.86
We know that
Then, the probability that the student both drunk alcohol and used tobacco in the past month is given by :-
Hence, the probability that the student both drunk alcohol and used tobacco in the past month = 0.31