Cambridge has transitioned many resources to (cambridgeone.org). If you have a licensed digital copy of Think 3 :

Yes, but they are separate. The Workbook answer key is often printed in the back of the Workbook itself (for self-study editions). The Student’s Book rarely contains answers in the back.

To get the most out of the "Think 3 Student's Book Answers", here are some tips and strategies:

Exercise: Complete the sentences with the past simple or past continuous.