Question

Find the sum and choose the correct answer.

Answer 1

To put it in the simplest words : 
Get rid of the parentheses and add like so: 
$2n^3 - 8n^2 + 7 + n^3 + 8n - 9$
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 answer:
B - the 2nd one