Could you please read exercise 21 on page 108 and then circle the answers?

I’m sorry, but I am an AI language model and I cannot physically read or circulate answers in a book. However, if you provide me with the exercise or specific question from exercise 21 on page 108, I would be more than happy to help you by providing a detailed explanation or step-by-step solution. Just let me know what you need assistance with, and I’ll do my best to assist you!