(n^2 - 9n^3 - 2) + (3n^2 + 4 - 6n^3) - (8n^2 + 7n + 5)

(n^2 - 9n^3 - 2) + (3n^2 + 4 - 6n^3) - (8n^2 + 7n + 5)

n^2 - 9n^3 - 2 + 3n^2 + 4 - 6n^3 - 8n^2 - 7n - 5

n^2+ 3n^2- 8n^2 - 9n^3- 6n^3 - 2+ 4- 5 - 7n

- 4n^2 - 15n^3 -3 - 7n