Of 50 students on a trip, 35 are student athletes and 5 are left handed. What is the probability that one of the students is an athlete or left handed?
Probability( Student Athelete or Left Handed Student) = Probability(Student Athlete) + Probability (Left Handed Student) - Probability (Left Handed AND Student Athlete)
Here, we have the probability of a left handed student, and the probability of a student athlete which are (5/50 => 1/10) and (35/50 => 7/10) , respectively.
We are not given the probability of a student who is BOTH left handed and a student athlete, so I am going to assume that all of the 50 students on the trip can only be left handed, a student athlete, or neither of the aforementioned characteristics.
Thus, we are left with (1/10) + (7/10) = (8/10) => .80 => 80% probability that one of the students is an athlete or left handed.