please look at the highlighted areas of the photo that i pasted below, for reference. this is a solution from CourseHero for the following question: based off of study: "among 143 subjects with positive test results, there are 24 false positive results; among 157 negative results, there are 3 false negative results. the question: 'if one of the test subjects is randomly selected, find the probability that the subject tested negative or used marijauna' HOW DID COURSE HERO GET 3/300 FOR P(A AND B)??

Step 1 of 2 Finding the individual probabilities. Let A denote the event that a subject tested negative and B denote the event that the subject used marijuana. We want to find P( A or B). P(tested negative)= number of subjects tested negative total number of subjects P(A) = 157 300 . P(used marijuana) = number of subjects who used marijuana total number of subjects P(A) = 122 300 . P(tested negative and used marijuana)= number of subjects tested negative and used marijuana total number of subjects P( A and B) 3 300 Step 2 of 2 Using addition rule to find the required probability. By the Addition Rule, P(A or B) = P(A) + P(B) - P(A and B). P( A or B) = 157_ 122 3 157+122-3 276 300 300 300 300 300 - 0.92