Giúp mik vs mik cảm ơn nhiều

2. How long has Kate been learning Japanese?

When did Kate start learning Japanese?

3. How long have you known Simon?

When did you first meet Simon?

4. How long have Rebecca and David married?

When did Rebecca and David start getting married? 

+) How long have/has S been V-ing

+) How long have/has S VPII/Ved

+) When did S start V-ing