George collected 50 marbles in white, yellow, green, and red. Half of them are white, and 12 are yellow. There are 50% fewer green balls than yellow balls. How many marbles are red? Let's answer step by step:
Half of the marbles are white, so there are 50 / 2 = 25 white marbles. Green marbles are only 50% as many as yellow marbles, so there are 50 / 100 * 12 = 6 green marbles. So currently we know that we have 25 + 12 + 6 = 43 marbles. The rest are red, so there are 50 - 43 = 7 red marbles. The answer: 7.