What's 21/16 simplified?

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Evaluate the following expression 1/3^2

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