Final answer:
You have 12 eggs in a 2/3 full 18-egg carton, and you need 6 more eggs to fill it. The fraction of the carton you need to fill is 1/3.
Step-by-step explanation:
If you have 2/3 of your first 18-egg carton full, this means you currently have 12 eggs in the carton, since 2/3 of 18 equals 12. To find out how many more eggs will fit in the carton, you subtract the number of eggs you have from the total capacity of the carton.
18 eggs (full capacity) - 12 eggs (current) = 6 eggs.
Therefore, you would need 6 more eggs to fill the carton. In fraction terms, you have 12/18 of the carton full, which simplifies to 2/3. To fill the carton exactly, you would need another 6/18 of eggs, which simplifies to 1/3.