Final answer:
The robin and blue jay will come to the bird feeder on the same day again after 15 days.
Step-by-step explanation:
To find out how many days it will be before the robin and blue jay both come to the bird feeder on the same day again, we need to determine the least common multiple (LCM) of 5 and 3.
The LCM is the smallest number that is divisible by both 5 and 3 without leaving a remainder.
The LCM of 5 and 3 is 15.
Therefore, it will take 15 days before the robin and blue jay both come to the bird feeder on the same day again.