It’s 29 to 9 (Official clock system).

20:31

It’s 29 to 9.

Correct answer

20:30

It’s half past 8.

Error: 1 minute earlier

19:53

It’s 7 to 8.

Error: read minutes starting from hour markings and adding minutes

18:40

It’s 20 to 7.

Error: confuse hour and minute hands