From 5 miles to 16 miles

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

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

If f(x) = 2x + 8 and g(x) = x4, what is (gº)?