Question

Use "Unless" instead of "If" and versa:

7. No one can help him if he doesn't tell the truth.

-> Unless ____________________________________

8. You will catch a cold unless you keep your feet dry.

-> If _________________________________________

9. Unless he phoned immediately, he wouldn't meet Mary.

-> If __________________________________________

Answer 1

he tells the truth, no one can help him.

you don't  keep your feet dry, you will catch a cold.

he didn't  phone immediately, he wouldn't meet Mary.

Answer 2

unless he  doesn't tell the truth , no one can help him

if you don't  keep your feet dry, you will catch a cold.

if he didn't  phone immediately, he wouldn't meet Mary.