Kelsey earns 7.20 an hour after school job. how much will she earn if she work 12 hours and 45 minutes

Should be $91.8 
how i got that is take $7.20 and times it by 12 and you get 86.4 and thats how much you would make it the 12 hours. Then you would take 7.2 divide by 60 and get .12 and thats how much you make in a min. so times it by 45 and you get 5.4 and youll add $86.4 and $5. and that equals too $91.8