1/He is too old to wear this coloured shirt

->He isn't young enough to wear this colored shirt

2/She is too weak to carry this box

->She isn't strong enough to carry this box.

3/This pen is too expensive for me too buy

->This pen isn't cheap enough for me to buy

4/Bill was too stupid to understand what I had said

->Bill wasn't smart enough to understand what I had said

5/ This bag is too heavy for her to carry

->This bag isn't light enough for her to carry

6/The test was too difficult for them to do

 ->The test wasn't easy enough for them to do

7/ I'm too poor to help you with the money

 ->I'm not rich enough to help you with the money

8/ This book is too dull to read

 ->This book isn't enough smart to read

9/ The room is too dark for us to study 

 ->The room isn't light enough for us to study

10/ The shelf is too high for her to reach

->The shelf isn't low enough for her to reach.