1. They wish they were traveling on comfortable buses

2. It's been a long time since we used these machines 

3. He hasn't seen his grandfather for 2 years, has he?

4. That bike hasn't been used for 2 years 

5. He said that those exercises could be done in fifteen minutes 

😊

It's a pity they are travelling on uncomfortable buses (wish)

-->I wish they weren't travelling on uncomfortable buses.

We haven't used these machines for a long time

--> it's the first time we have used these machines for a long time.

He last saw his grandfather 2 years ago,didn't he?

--> he hasn't seen his grandfather for 2 years.

The last time I used that bike was 2 years ago

--> That bike hasn't used for 2 years. 

He said that "I can do these exercises in fifteen minutes"

--> He said that those exercises could be done by him in fifteen minutes.