###Human: 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?, ### Assistant: 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. 
 So the answer is :  7