a problem and solution

[jas_fluidm]

A parking lot contains 80 vehicles. Each vehicle is either a car or a truck, and each vehicle is either red or green.  35 vehicles are red, and 60 vehicles are cars. If there are 9 green trucks, how many red cars are there?
sol: 80-60=20
      20-9=11
      35-11=24
hence ans is 24.

[Saba Fatema]

Interesting.