janice went out to eat and bought a hamburger, a bag of chips,
and a drink. the hamburger cost $2.57, and the chips cost $1.25.
janice gave the cashier $20.00 and received $14.39 in change.
how much did the drink cost?

Ben frank is an electrician who installs lighting fixtures. he charges (in dollars) his clients 15h+40f15h+40f where hh is the number of hours worked and ff is the number of fixtures installed. how much does ben frank charge when he works 77 hours and installs 99 fixtures?