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 [tex]P(A\cap B)=P(A)+P(B)-P(A\cup B)[/tex]
Then, the probability that the student both drunk alcohol and used tobacco in the past month is given by :-
[tex]P(A\cap B)=0.84+0.33-0.86=0.31[/tex]
Hence, the probability that the student both drunk alcohol and used tobacco in the past month = 0.31