I think you skipped the math classes I'll fix this for you:I think I fixed it.
Mini Cooper Classic - 4
VW New Beetle - 2
Ford F-350 - 3 (-1)
Ford Mustang GT - 4
Ford Mustang Cruiser - 6
Ford Mustang Fastback - 7
Panoz Roadster - 7
Freightliner Century - 2 (-1)
New Mini Cooper - 2
Audi TT - 5
Aston Martin DB7 Vantage - 5
Panoz GTR-1 - 6 (+1)
American LaFrance Fire Truck - 4
1959 Cadillac Eldorado - 6