PLEASE HELP THIS IS ALL IT GIVES ME I HOPE YOU COULD DK THE ANSWER WITH JUST THIS BUT PLEASE I NEED HELP

Answer:
f (3) = 21
Step-by-step explanation:
To answer, we know that x in f (x) equals 3, so in f (x) = 7x, we simply substitute x with 3:
f (3) = 7 (3)
Now multiply:
f (3) = 21
21 is your answer
Hope this helps :)