James has a collection of 20 miniature cars and trucks. Cars make up 40% of the collection. If James adds only cars to his collection, how many cars must he add to make the collection 75% cars?
+36916 20 in the collection .4 (20 ) = cars = 8 cars
add x number of cars to the collection to make it 75% cars
(20 + x)(.75) = 8+x
15 + .75x = 8 + x you can take it from here ! 
