Question

1. I will be sad if he doesn't study harder

-> Unless

2. Why don't you install a burglar alram in your house ?

-> I suggest

3. You won't find ny accommodation if you don't book it in advance

-> Unless

Answer 1

1. I will be sad if he doesn't study harder

-> Unless he studies harder,i will be sad

2. Why don't you install a burglar alram in your house ?

-> I suggest that you should install a burglar alram in your house.

3. You won't find my accommodation if you don't book it in advance

-> Unless you book my accommodation in advance,you won't find it