Helen rented a kayak at the lake. there is a charge of $6 as an initial fee and then $3 an hour for every hour that she uses the kayak. if the total charge is $21, how many hours did she kayak?

Me its important ! marge runs an ice cream parlor. her speciality is triple chocolate sundaes.she can prepare 1 sundae every 2 minutes, and she earns $1.20 for each sundae she makes . if she just makes sundaes for a single shift of at most 4 hours and at least 2 hours , which function relates her earnings to the number of minutes she works?