Find the sum and choose the correct answer.

(2n 3 - 8n 2 + 7) + (n 3 + 8n - 9)

3n3 - 2
3n3 - 8n2 + 8n - 2
2n6 - 8n2 + 8n - 2
3n6 - n - 2

To put it in the simplest words : 
Get rid of the parentheses and add like so: 

Combine like terms
2n^3+n^3= 3n^3
-8n^2 remains the same since there are no like terms for it
8n also remains the same
-9+7=-2
Put all of the numbers together
3n^3-8n^2+8n-2
Final
B - the 2nd one