1. I didn't eat lunch, i feel hungry now
-> if i .....had eaten lunch, I wouldn't feel hungry now .........
2. if hadn't rained, we would have a better crop
-> but for....rain, we would have a better crop.......
3. if you want my advice, i wouldn't buy it
-> if i ...were you, I wouldn't buy it ........
4. i only come if they invite me
-> unless.......they invite me, I will come.........
5. he didn't revise all his lesson, he failed the exam
-> if he .......had revised all his lesson, he wouldn't have failed the exam........