In the jar, there are 7 blue marbles, 11 red marbles, and some yellow marbles. If the chance of randomly picking a yellow marble is 1/4, how many yellow marbles are there? Let's answer step by step:
Let y be the number of yellow marbles. There are 11 + 7 + y = 18 + y total marbles. y / (18 + y) = 1 / 4. 4y = 18 + y. 3y = 18. y = 6. There are 6 yellow marbles. The answer: 6.