to get the ratio first add both sides of the ratio then divide it by the number of the cars then you get a 30 per 1 ratio so then if you times 30 to 3 that means it is 90 and then there are 150 blue cars using that math and to make sure that is right you can check it by adding the total red cars and blue cars you got. 150 + 90 = 240 which is the total. so your answer is 90 Red Cars
