#### Answer

B. 18n + 20

#### Work Step by Step

Since there is a one time entrance fee of 20 dollars, "+ 20" must be in our equation. It's not "20n" because the 20 dollar fee does not occur every night.
However, the 18 dollar fee occurs every night, so "18n" must be in our equation.
Combining both parts, you get: 18n + 20
You pay 18 dollars for each night you stay, in addition to the 20 dollar entrance fee.