Answer:
Therefore, there is at least one class in which two people are wearing the same color shirt
Step-by-step explanation:
Proof: (By contradiction).
Suppose that, in each of the 8 classes, no two people wear the same color shirt.
Notice that, if there are 4 people in a class, then at least two of them are wearing the same color shirt
because they can only pick between 3 colors.
Hence the number of people in a class must be at most 3.
Since there are 8 classes, then the total number of attendees is at most 24.
A contradiction. Since the problem says there are 25 people attending yoga classes.
Therefore there is at least one class in which two people are wearing the same color shirt
