Final answer:
To find when Rami will have both swimming and guitar lessons on the same day again, we need to find the least common multiple (LCM) of 3 days and 7 days. The LCM of 3 and 7 is 21. Therefore, Rami will have both swimming and guitar lessons on the same day again after 21 days.
Step-by-step explanation:
To find when Rami will have both swimming and guitar lessons on the same day again, we need to find the least common multiple (LCM) of 3 days and 7 days.
The LCM of 3 and 7 is 21. This means that Rami will have both lessons on the same day every 21 days.
Therefore, Rami will have both swimming and guitar lessons on the same day again after 21 days.