Baxter has received a grant to run an environmentally sensitive parking lot downtown. To encourage carpooling, he charges $20 per day per vehicle with only the driver in it and $10 per day for each carpool vehicle with two or more people. On one Monday, 115 vehicles were parked in his lot, and he took in $1990. How many of each kind of vehicle used the lot that day?
and c = 115 – s the number of carpool cars.
20s + 1150 – 10s = 1990
10s = 840
s = 84
c = 115 – s = 31