1.How long is it since they bought the house ?
⇒ When did they buy the house?
2.It's years since we decorated this room.
⇒ We haven't decorated this room for years.
3.Laurence hasn't seen his sister since she left for Japan.
⇒ Laurence last saw his sister when she left for Japan.
4.My sister has studied French fer 2 years
⇒ My sister began studying English two years ago.
5.When did Catherine and Henry get engaged?
⇒ How long have Catherine and Henry been engaged?