UPSC Civil Services 2019 Prelims General Studies Paper II

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