You are counting black and blue cars in the school parking lot. You see a total of 39 cars in the lot. There are 11 more black cars than blue cars.
How many are there of each color car?

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?