Either Past or Present Tense

[kahhong]

Dear All,
I dont know whether use past or present tense for something that happen in past carry until present..
for an example: i dont know how to do particular homework on past until now... i should use i dont understand how to do that homework or i did'nt understand how to do that homework.
which one correct?
Best Wishes,
-kahhong

[Tdol]

Do you understand know?

[irene8]

Well i think that the first is more correct : i don't understand
(But I'm beginner )

[Tdol]

What I wanted to know was whether the person in the sentence now understands how to do the work.
I don't understand how to do the homework.
If the person is asking for help, then this is the natural sentence. The time isn't really important- what matters is finding out, so using the present shows that they have a problem now.
I didn't understand how to do the homework.
Here, the problem is in the past, and the person didn't get to understand how to do it, but the time has passed.