In a group of 18 people, 10 read French, 11 read English, while 6 read none of these two. How many of them read both French and English ?

The correct answer is (B) 9.

Set theory calculation:

• Total population in the group ($U$) = 18.
• People reading neither French nor English = 6.
• Number of people reading at least one language: $n(F$$\cup$ E) = 18 - 6 = 12.
• Given: French readers $n(F) = 10$, English readers $n(E) = 11$.
• Using inclusion-exclusion formula: $n(F$$\cap$ E) = n(F) + n(E) - n(F $\cup$ E).
• $n(F$$\cap$ E) = 10 + 11 - 12 = 21 - 12 = <strong>9</strong>.
• Therefore, 9 people read both French and English.