Given: 8 friends can read French book, 18 can read Spanish book and 9 can read Russian book. 2 friends in the group can read two languages book and one friend can read all the three languages book Calculation: Let us assume the two friends who can read two languages book speak Spanish and French. The third friends then read all the three languages book. Number of friends who can read French book = 8. Only read French book = 8 – 2 – 1 ⇒ 5 Number of friends who can read Spanish book = 18. Only read Spanish book = 18 – 2 – 1 ⇒ 15 Number of friends who can read Russian book is 9. Only read Russian book = 9 – 1 ⇒ 8 Thus the number of friends who can read only one language book ⇒ 5 + 15 + 8 ⇒ 28 Number of Friends who can read two languages book = 2 Number of friends who can read all the languages = 1 Total number of friends ⇒ 28 + 2 + 1. ⇒ 31 ∴ There are in the group 31 friends.