1. She doesn't live in London because she doesn't know anyone there.

=> She'd ....................live in London if she knew someone there...................

2. I can't live in the country because i can't find a job there.

=> I'd ………………live in the country if I could find a job there…………………
 

Peter gets bad marks because he doesn't prepare his lesson well

=> If Peter ……………prepared his lesson well, he wouldn't get bad marks…………