It’s 21 to 11 (Official clock system).

10:39

It’s 21 to 11.

Correct answer

10:40

It’s 20 to 11.

Error: 1 minute later

09:53

It’s 7 to 10.

Error: read minutes starting from hour markings and adding minutes

08:50

It’s 10 to 9.

Error: confuse hour and minute hands