It’s 17 to 8 (Official clock system).

19:43

It’s 17 to 8.

Correct answer

19:42

It’s 18 to 8.

Error: 1 minute earlier

18:49

It’s 11 to 7.

Error: read minutes starting from hour markings and adding minutes

21:35

It’s 25 to 10.

Error: confuse hour and minute hands