Answer....
Is Ken going to take his driving test ?
No( fail) If he.......

Why dont we stay at a hotel?
No.( cost too much ) If.....

Is Sally going to apply for the job?
No.( not/getit) If.......

Lets tellfthem the truth.
No.( not/believe us) If......

Why dont we invite Bill to the party.?
No.( have to invite his friends too)

If Ken takes his driving test he will fail it.
If we stay in the hotel it will cost too much.
If Sally applies for the job she won't get it. (или If Sally doen't apply for the job she won't get it)
If we tell them the truth they won't believe us.
If we invite Bill to the party we will have to invite his friend too