Answer:
4
Step-by-step explanation:
Let's start with the easiest bits.
We know the probability of drawing a red card is 1/4, this means every four cards there is one red. So, 12/4 = 3, there are 3 red cards in the 12 card pile.
Next, we are also given the probability of drawing a blue card us 1/12. In the same fashion, we can figure out there is 1 blue card.
Finally, we are told the probability of drawing a green card is the same as drawing a yellow card. Therefore there is the same amount of green cards as yellow.
There are 8 cards left that are green or yellow, as 12 - 1 - 3 is 8. 8/2 is 4, so there are 4 green cards in the box.
Hope this helps!