He's not strong enough to lift that box.

He's too weak to lift that box.

1. He isn't old enough to vote. 
    He is to vote.
2. Algebra is too difficult for me to understand.
    Algebra isn't for me to understand.
3. I can't drink this tea. It's too cold.
   It's not .
4. The weather is not warm enough to go swimming.
    The weather is to go swimming.
5. This book isn't easy enough for the children to read.
    This book is for the children to read.
6. That shirt is too small for me to wear.
     That shirt isn't for me to wear.
7. The watch was too expensive for him to buy.
     The watch wasn't for him to buy.
8. It's not quiet enough in here to speak. Let's go out!
    It's in here to speak. Let's go out!