Explanation:

- You have 12 numbers with an average of M.

- The sum of all 12 numbers is $12M$.

- For 8 of those numbers, the average is P.

- The sum of those 8 numbers is $8P$.

- The remaining 4 numbers then have a sum of $12M-8P$.

- If the average of these 4 numbers is N, then their sum is $4N$.

- Thus, we have the equation $12M-8P=4N$.

- Dividing the whole equation by 4 gives $3M-2P=N$, which can be rearranged to $3M=2P+N$.

Option 1: 3M = 2P + N