1.Many teenagers can't dective when to study and when to play.
=Many teenagers can't dective when (they should study) and when (they should play).
2.Why not go to the cinema with us?
=(What/How about) going to the cinema with us?
1.Many teenagers can't dective when to study and when to play.
=Many teenagers can't dective when (they should study) and when (they should play).
2.Why not go to the cinema with us?
=(What/How about) going to the cinema with us?