Ответ:
1.
-How long have you studied English?
-I've studied English for 10 years.
2.
-How long have you been at this school?
-We've been at this school for 6 years.
3.
-How long has your family lived in this town?
-My family has lived in this town since 1999.
4.
-How long has this school been here?
-This school has been here since 1950.
5.
-How long has your friend had a computer?
-My friend has had a computer for 10 years.
6.
-How long have you liked sport?
- I've liked sport since my childhood.