Ответ:

1. If Gemma didn't know good English, she couldn't work in London.

2. I would go into town if my doctor's appointment weren't this morning.

3. I wouldn't go out if I were you - it's snowing.

4. If Mum weren't so busy, she'd help me this morning.

5. I wouldn't buy this T-shirt if I didn't really like it.

6. I would go to football practice if I had time.

7. I couldn't call my mum if I didn't have my mobile phone.