Which ones are linear and non-linear equations

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

Find the value of the variable and the length of each secant segment.

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.