"Everything is bad but I know what to do."
Translation:Всё плохо, но я знаю, что делать.
Why is "Все плохо а я знаю, что делать." incorrect? This sentence seems to have a contrast which would suggest the use of 'a' rather than 'но' as given in the correction. Thank you.
It is not a contrast. It is more like having an ability to change something. For example, "Everything is bad but Tom is happy" has a contrast, and can be translated with "а", but not the sentence in the task.