1.Minh hasn't written to his penpal for five month

2.I haven't visited Kuala Lumpur for 3 years

3.How long have you studied English?

4.They have built this house for 2 months

 
5.My father has worked in this factory since last week

6.When did he begin to work in the garden?

7.He has leant English since he was 18

8.They began to work in that factory 5 years ago