To simplify the expression 5^n + 2 - 5^n / 5^n + 1 + 5^n - 18 * 5^(n-1), we can combine like terms and use the properties of exponents.

First, let's simplify the expression step by step:

Combine like terms:
5^n + 5^n + 5^n = (3*5^n)Combine like terms with numbers:
(3*5^n) - 18 = 3(5^n) - 18Simplify the expression:
5^n + 2 - 5^n / 5^n + 1 + 3(5^n) - 18
= 2 + 1 + 3(5^n) - 18
= 3 + 3(5^n) - 18
= -15 + 3(5^n)

Therefore, the simplified expression is -15 + 3(5^n).