1.    If Minh were more careful,he would get better marks.
=>.if minh werent more careful, he wouldnt get better mark
2  If they hadn’t thrown rubbish in the forest, they wouldn’t have been fined..
if they had thrown rubbish in the forest, they would have been fined.
3.    If the factory were closed, millions of people would be out of work.
=>if the factory werent closed, millions of people wouldnt be out of work
4.    If he shares his feelings, he will feel more relieved. 
 =>If he dont share his feelings, he wont feel  more relieved
5.If Nam studies harder he will pass the final exam.
=>If nam doesn't studies harđre he will fall the final exam.