simply, please. cuz i cant get it myself. lol

Answer:
21x + 28
Step-by-step explanation:
open the bracket
=21x + 4
Answer:
well there might me an answer either u can put 21x +28 or 14x, but go with 21x + 28
Step-by-step explanation:
you multiply 3x time 7 and 4 times 7 since u cant add 3x plus 4 and to separate it to get a simpler expression