1. I am not hungry, so I don't eat anything

-- If I were hungry, I would eat something.

2. She learns badly because she never does her homework.

-- If she did her homework, she would learn well.

3. He is not thirsty, so he does not drink the water

-- If he were thirsty, he would drink the water.

4. We didn't do the test well because we didn't review the lesson carefully

-- If we had reviewed the lesson carefully, we would have done the test well.

5. If he doesn't invite me, I will not come

-- Unless he invites me, I won't come.