ex 8 : it takes me half an hour to get to work 

1/ If I have spare time , I will see you off at the airport.
-->Unless I don't have spare time, I will see you of at the airport.
2/ It was too hot for us to go out .
-->Because it was too hot, we can't go out.
3/ You don't have breakfast. You are hungry and tired
-->If you don't have breakfast, you will be hungry and tired.
5/You get up before 6 a.m or you will miss the train.
--->If you don't get up before 6 a.m, you will miss the train.

1> If I have spare time , I will see you off at the airport.
-->Unless I don't have spare time, I will see you of at the airport.
2> It was too hot for us to go out .
-->Because it was too hot, we can't go out.
3> You don't have breakfast. You are hungry and tired
-->If you don't have breakfast, you will be hungry and tired.
5>You get up before 6 a.m or you will miss the train.
--->If you don't get up before 6 a.m, you will miss the train.