Number of people who read either or both languages. = 15 – 3 = 12.
∴ a + b + c = 12 Number of people who read French, a + b = 7 Number of people read English, b + c = 8 ∴ (a + b) + (b + c) = 7 + 8 = 15 ⇒ (a + b + c) + b = 15 ⇒ 12 + b = 15 ⇒ b = 3 ∴ a = 4 and c = 5 Hence, number of people who can read exactly one language = a + c = 9