8.7. In the city of Bukvinsk, people are acquainted only if their names have the same letters, otherwise - they are not. Several residents of Bukvinsk were asked how many acquaintances they have in the city. Martin said 20, Klim - 15, Inna - 12, Tamara - 12. What did Camilla answer?
Answer: 15 acquaintances

Solution. Note that all five students listed in the condition are acquainted with each other. Therefore, Martin has 16 acquaintances outside this group, while Inna and Tamara each have 8. However, all of Inna's acquaintances are acquainted with Martin, and all of Tamara's acquaintances are also, with no other acquaintances for Martin. Since $16=8+8$, there are no common acquaintances of Inna and Tamara outside our group. Their common acquaintances can only be people with the letter A in their name, so there are no such people outside the considered group. In this case, Camilla is acquainted with exactly the same people as Klim (and they are also acquainted with each other), meaning she has 15 acquaintances.