It does not take them 15 minutes to read the text.
Does it take them 15 minutes to read the text?
It takes them 15 minutes to read the text, does not it?
How long does it take them to read the text?
What takes them 15 minutes?
It took him an hour to get there, didn't it?
How long did it take him to get there?
Did it take him an hour to get there?
For whom did it take an hour to get there?
It didn't take him an hour to get there.