Let's say that set E is the set of students who passed in English and set H is the set of students who passed in Hindi. It is given that N = 120, n(E) = 75, n(H) = 50 and n(E ∩ H) = 30. Number of students who passed in English ONLY: = n(E) - n(E ∩ H) = 75 - 30 = 45. Number of students who passed in Hindi ONLY: = n(H) - n(E ∩ H) = 50 - 30 = 20. Total number of students who passed in only one subject: n(A) = 45 + 20 = 65. Required probability =