Answer:
D. 3x + 12
Step-by-step explanation:
Distribute the 3 inside.
3 * x = 3x
3 * 4 = 12
3x + 12
3x+12 (D)
3(x+4)
=(3)(x+4)
=(3)(x)+(3)(4)
=3x+12
Hope this helps!