Can anyone me with these problems, i am having a very hard time doing them and i know they are a lot but it is very confusing

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

Just tell me how to set up the equation.

Abacteria population is tripling every hour. by what factor does the population change in 1/2 hour? select all that apply