Answer: The answer is 10.
Step-by-step explanation: The recursive formula of the sequence is given by
[tex]f(n+1)=f(n)-2.[/tex]
We are to find the value of f(5) if f(1) is 18.
We have
[tex] f(2)=f(1)-2=18-2=16,\\\\f(3)=f(2)-2=16-2=14,\\\\f(4)=f(3)-2=14-2=12,\\\\f(5)=f(4)-2=12-2=10.[/tex]
Thus, the value of f(5) is 10.