It’s 21 to 8 (Official clock system).

07:39

It’s 21 to 8.

Correct answer

07:40

It’s 20 to 8.

Error: 1 minute later

06:53

It’s 7 to 7.

Error: read minutes starting from hour markings and adding minutes

08:35

It’s 25 to 9.

Error: confuse hour and minute hands