Answer:
The number that fits that belongs in the green box is 3n^2
The whole expression answer is: 3n^2 + 6n +4
Explanation:
You can add the like terms together.
1. Since there is only one n^2 term you can keep the 3n^2
2. There are two n terms ( 5n and n ) so you can add them together to get 6n
3. There is only the number 4 left so you can keep it.
The solution is 3n^2 + 6n +4