Which is a function which isnt one ?

Sara needs to take a taxi to get to the movies the taxi charges $4.00 for the first mile and then $2.75 for each mile after that if the total charge is $20.50 then how far was sara’s taxi ride to the movie

Check all that apply. f is a function. f is a one-to-one function. c is a function. c is a one-to-one function.

What is the following sum in simplest form? square root 8 + 3 square root 2 + square root 32