1. Saya tidak boleh jawab soalan itu.
[I cannot answer that question]
2. Saya tidak dengar suara ibu saya dari dapur.
[I did not hear my mother’s voice from the kitchen]
A student asks: Why the second sentence does not contain ‘boleh’?
Boleh implies ‘could’ and the first sentence suggests that you could not answer the question because you don’t have the answer.
The second sentence suggests that you did not hear the voice of the mother simply because she was far away.
The first one with boleh has a (mental) capability issue whereas the second one is a circumstantial issue.