Answer:
Family stayed at park for 11 nights.
Explanation:
State park charges entrance fees = $20
In addition to this fees it charges per night for camping = $18
If a family spends x nights in the park for night camping then charges
= $(20 + 18x)
A family spends a total of $218 for night stay
then 218 = 20 + 18x
18x = 218 - 20
18x = 198
x =

x = 11
Therefore, family stayed at park for 11 nights.