There are 3 meatballs on each spaghetti plate. If Theresa's 3 sons each eat two-thirds of the meatballs on their respective plates, how many meatballs are still left on their plates altogether? Let's answer step by step:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Total meatballs on the plates 3 x 3 = 9. If two - thirds are eaten, one - third remaining on the plates is 9 / 3 = 3. The answer: 3.