1. Mixed

   
   

2. Both weigh the same

   
   

3. Olivia, Sam, Tanya, Carlos
   

   
   

4. Tomorrow
   
   

5. His children

   
   

6. 12
   

   
   

7. No answer: It could be either Clara or Ava
   
   

8. 8
   

   
   

9. 3/5
   

   
   

10. What door will the other door tell me to go through? (And go through the other one.)

Solve all problems before looking at the answers.