It’s 21 to 12 (Official clock system).

11:39

It’s 21 to 12.

Correct answer

11:40

It’s 20 to 12.

Error: 1 minute later

10:53

It’s 7 to 11.

Error: read minutes starting from hour markings and adding minutes

08:55

It’s 5 to 9.

Error: confuse hour and minute hands