Final answer:
Juan can put all nine quarters into his red bank, which equates to $2.25.
Step-by-step explanation:
The question asks us how many quarters Juan can put in his red bank, and we know that he has nine quarters. This is a straightforward question, and the answer is simply the amount of quarters Juan has, as there is no mention of any limitations on the capacity of the red bank.
The calculation or consideration required here is minimal. If Juan has nine quarters, he can put all nine quarters into his red bank, assuming the bank can hold at least that many. It's also worth noting that four quarters make up a dollar, so Juan has a total of $2.25 in quarters.