ALGEBRA
posted by el chave del ocho .
I went to the car show this weekend and that is what I saw: Every red car was a sport car, but I found it odd that half of all the blue were sports cars. A salesman told me that half of all the sports car were red. I counted 40 blue cars and 30 red cars. How many sports cars were neither blue nor red?

Red = sports
30 red cars => 30 sports cars
Half of sports cars were red => 60 sports cars
Half of blue cars were sports cars and there are 40 blue cars => 20 blue sports cars.
Out of 60 sports cars, 30 were red, and 20 were blue. So ... 
I don't really know but I think 10 cars weren't blue or red