At the end of a party,

3 pizzas  /  (2/8 pizza/person)=

3 x 8/2 people = 12 people

one person: $\frac{2}{8}$ of a pizza, or $\frac{1}{4}$ of a pizza.

Since we have $3$ pizzas, there will be $\frac{3}{\frac{1}{4}}=3*4=\boxed{12}$ people.