Can someone help me with these...plz

Simplify

2radical (12) + 4 radical (27)

if i simplify radical (12) i get 2radical (3) then if i simplify radical (27) i get 3radical (3). so now i don't know if i'm doing this correctly or how to set it up...

2 sqrt 12 + 4 sqrt 27
4 sqrt 3 + 12 sqrt 3
16 sqrt 3

how did you do this can you explain it to me please. I want to really understand this type of math...But i am just not seeing it...Can you explain to me the steps that you did please...