Answer:
D
Step-by-step explanation:
The thing that is being cubed here is the sum of x and 4, not x or 4 individually. After you have taken care of what is in parentheses, you add 3x, which gives the sum of x+4 cubed and 3x. Hope this helps!
(x + 4)³ is x + 4 cubed
(x + 4)³ + 3x is the sum of x + 4 cubed and 3x
