`28.` How long is it since he wrote to me?

`->` How long is it + since + S + V2/ed?

`=` When + did + S (first) + V?

`29.` I have worked for this company for a year.

`->` S + have/has + Vpp + for/since + time

`=` S + started/began + V-ing/to V + time + ago

`30.` Jack has taught English for 10 years.

`->` S + have/has + Vpp + for/since + time

`=` S + started/began + V-ing/to V + time + ago

It is 10 years since Jack started teaching English.

`->` S + have/has + Vpp + for/since + time

`=`  It is + time + since + S + started/bagan + V-ing/to V

`31.` Jane has lived here since 2000.

`->` S + have/has + Vpp + for/since + time

`=` S + started/began + V-ing/to V + time + ago

`32.` Joe has been a vegetarian since 2010.

`->` S + have/has + Vpp + for/since + time

`=` S + started/began + V-ing/to V + time + ago

`33.`  The last time we smoked was 3 months ago.

 We haven't smoked for 3 months ago.

It's 3 months since we (last) smoked.

`->` S + have/has + not + Vpp + for/since + time

`=` It is + time + since + S (last) + V2/ed

`=` The last time + S + V2/ed + was + time + ago

`=` S + last + V2/ed + time + ago