Answer:
3
Step-by-step explanation:
The notation "f(4)" means you put 4 where x is in the algebraic expression, then do the arithmetic.
f(4) = 2·4 -5
= 8 -5
= 3
Six million seven thousand two hundred
Six point eight four.
(Note, you don't say, "Six point eighty-four" As it doesn't sound correct.
Cheers.