1.I don’t know how to use a computer, so I don’t buy it.
→ If I knew how to use an computer, I would buy it
2.My brother is not here, so he can not help me with my essay.
→ If my brother were here, he could help me with my essay
.3.Because I don’t have much money, I will have to stay here.
→ If I had much money, I wouldn't have to stay here
4.I am not an environmentalist, so I can’t ask them to stop dumping chemical waste into this river. →If I were an environmentalist, I could ask them to stop dumping chemical waste into this river
5.Because her cousin can’t speak Japanese, he won’t apply for that good job.
→If her cousin spoke Japanese, he would apply for that good job