It’s 21 to 10 (Official clock system).

09:39

It’s 21 to 10.

Correct answer

09:40

It’s 20 to 10.

Error: 1 minute later

08:53

It’s 7 to 9.

Error: read minutes starting from hour markings and adding minutes

08:45

It’s a quarter to 9.

Error: confuse hour and minute hands