Question:
A bag contains 12 black, 18 yellow and 30 purple marbles.
Last updated: 7/13/2022
![A bag contains 12 black, 18 yellow and 30 purple marbles.](https://media.kunduz.com/media/sug-question/raw/58596380-1657737725.5916297.jpeg?h=512)
A bag contains 12 black, 18 yellow and 30 purple marbles. Joe pays $10 for the opportunity to pick a marble from the bag. If he picks a black marble, he gets $20. If he picks a yellow marble, he gets $15. If he picks a purple marble, he gets $k. The game is fair. Find the value of k. Give an exact answer.