Final answer:
Antonio can buy 4 containers of milk for the event.
Step-by-step explanation:
To represent the number of containers of milk Antonio can buy, we can use the inequality $3c ≤ $12, where c represents the number of containers. To determine whether Antonio can buy 4 containers, we substitute c with 4 in the inequality: $3(4) ≤ $12. This simplifies to 12 ≤ 12, which is a true statement. Therefore, Antonio can buy 4 containers of milk for the event.