Question

1,He lost everything because he is careless 
=> if...................................................................
2,she left him because he behaved badly 
=> if he..............................................................
3,if lan doesn't do exercises,she will get terribly ill
=>unless................................................................

Answer 1

1,He lost everything because he is careless 
=> if he weren't careless, he wouldn't lose everything.
2,she left him because he behaved badly 
=> if he hadn't behaved badly, she wouldn't leave him.
3,if lan doesn't do exercises,she will get terribly ill
=>unless Lan does exercises, she will get terribly ill.