As we are given with 
Now using the change of base property ,we can re-write

Each log has base of 10

Pardon my handwriting lol
Step-by-step explanation:
I don't think I understand the question
Would assume:
f(n + 1) = f(n) - 2
f(2) = f(1 + 1) = f(1) - 2 = 18 - 2 = 16
<span>f(3) = f(2 + 1) = f(2) - 2 = 16 - 2 = 14
</span>
<span>f(4) = f(3 + 1) = f(3) - 2 = 14 - 2 = 12
</span>
<span>f(5) = f(4 + 1) = f(4) - 2 = 12 - 2 = 10
</span>
f(5) = 10
Answer:
45
Step-by-step explanation: