1. If Margaret doesn't give up smoking, she will get lung cancer.
Uniless .Maragart gives up smoking, she will get lung cancer.
2. if you don't sign the contract, you won't make a lot of
money.
Unless .you sign the contract, you wont't make a lot of money
3. if he doesn't answer correctly, that student will fail
the exam
Unless he..answers correctly, that student will fail the exam
4. If you are not careful, you will cut yourself with that
knife.
-> Unless .you are careful, you will cut yourself with that knife