Answer:
3 more red marbles
Step-by-step explanation:
When you add up all of the marbles, there are 13 marbles.
The objective is to have the probability of selecting a blue marble from the bag to be 1/4. Since there are 4 blue marbles and 4 is 1/4th of 16, 16-13 is 3 so you add 3 more red marbles to have that chance.
I hope this helps!!!
