6x² + 48x + 96
6(x² + 8x + 16)
6(x + 4)(x + 4) is your polynomial fully factored so I'm guessing the binomial you're looking for is (x + 4).
Answer:

Step-by-step explanation:
In 5 liters, there is 4% salt.
Lets find liters of salt.
First, converting 4% to decimal (dividing by 100):
4% = 4/100 = 0.04
0.04 * 5 = 0.2
So, there is 0.2 liters of salt.
Now, x liters of water is added to total, so total is now:
5 + x
The concentration of salt will be amount of salt divided by amount of salt water solution.
Amount of salt = 0.2 (as seen above)
Amount of new salt water solution = x + 5
So,
Concentration of salt in new solution is 
2nd choice is right.