Write a real world problem of Simplifying Exponent Expressions and solve (also how you did it)

Which math sentence can be used to determine if the triangle is a right triangle?

Tom wants to order tickets online so that he and three of his friends can go to a water park the cost of the tickets is 16.00 per person there is also a 2.50 one-time service fee for ordering tickets online write an expression in term of n that represents the cost for n ordering tickets online

I’m still confused on how to work the percentages