3. The answer is $(\mathbf{A})$.

Let $N$ be the number of Pietro and Paolo's friends who attend the pizza party (excluding Pietro and Paolo themselves). The dinner bill in Euros must equal both $12(N+2)$ and $16N$. Setting these two quantities equal gives $12N + 24 = 16N$, from which we find $N=6$.
3) Pietro and Paolo are celebrating their name day at a pizzeria with their friends. At the end of the dinner, the bill is divided equally among all those present, and each person should pay 12 Euros. However, with great generosity, the friends decide to treat Pietro and Paolo to dinner; the bill is divided equally among Pietro and Paolo's friends (i.e., all those present except Pietro and Paolo), and each of them pays 16 Euros. How many friends do Pietro and Paolo have?
(A) 6,
(B) 8,
(C) 10
(D) 12, (E) 16.