1. I don’t know enough about the machine, so I can’t mend if myself.

If I knew enough about the machine,I could mend if myself.

2. He didn’t prepare for the interview, so he won’t get the job.

If he had prepared for the interview, he would have got the job.

3. Not enough money is spent on cancer research, so a prevention has not been found.

If more money were spent on cancer research, a prevention would have been found.

4. Andrew wants to ask the singer for his autograph, but he isn’t brave enough.

If Andrew were brave enough, he would ask the singer for his autograph.

5. We live in a town. I can’t have a garden.

If we didn't live in a town, I could have a garden.