Answer:
6n + 18
Step-by-step explanation:
Multiply each n and 3 by 6:
6 (n+3) = 6n + 18
15+n
(6+n) + (6+3)
(6+n) + 9
(6+9) + n
15 + n
Don't take just my answer, I am not completely positive this is right.
