I don’t know her number, so I don’t phone her.
If I knew her number, I would phone her.

I lose the key, so I cannot get into the house.
If I didn’t lose the key, I could get into the house.

The house is very large, that's why they couldn’t paint it in a week.
If the house weren’t so large, they could paint it in a week.

Peter is fat because he eats so many chips.
If Peter didn’t eat so many chips, he wouldn’t be fat.

He can’t go out now because he studies for the exam.
If he weren’t studying for the exam, he could go out now.

I need to finish the homework, so I can’t hang out with friends.
If I didn’t need to finish the homework, I could hang out with friends.

She is lazy, so she can’t pass the exam.
If she weren’t lazy, she could pass the exam.

Since my boss doesn’t let me take a rest, I feel exhausted now.
If my boss let me take a rest, I wouldn’t feel exhausted now.

I don’t buy this car because it wastes too much money.
If it didn’t waste so much money, I would buy this car.

The weather is not good today, so we can’t go out for a walk.
If the weather were good today, we could go out for a walk.

As they don’t tell her the truth, she is very upset now.
If they told her the truth, she wouldn’t be very upset now.

I don’t know Ronald’s address, so I can’t send him the invitation.
If I knew Ronald’s address, I could send him the invitation.