III/1. I'm not rich, so I don't live in a big house.

→ If I were rich, I would live in a big house.

2. We don't visit you very often because you live so far away.

→ We would visit you very often if you didn't live so far away.

3. Sandra can't take a photo because she hasn't got her camera. 

→ Sandra could take a photo if she got her camera.

4. She buys a lot of clothes, so she has no money.

→ If she didn't buy a lot of clothes, she wouldn't have no money/ she would have money.

5. I have to work tomorrow evening, so I can't meet you.

→ If I didn't have to work tomorrow evening, I could meet you.

6. It's raining, so we can't have lunch in the garden.

→ If it weren't raining, we could have lunch in the garden.

7. I'm often tired in the morning because I go to bed late.

→ I wouldn't be tired in the morning if I didn't go to bed late.

8. We haven't got a calculator, so we can't work this our quicker.

→ If we had got a calculator, we could work this our quicker.

9. Do the test carefully or you may get bad mark.

→ If you don't do the test carefully, you may get bad mark.

9. Come soon or you may not meet us.

→ If you don't come soon, you may not meet us.

10. Hurry up or we will miss the bus. 

→ If we don't hurry up, we will miss the bus.

11. I don't have the key, so I can't get into the house.

→ If I had they key, I could get into the house.