楼主你好啦！
我举几道中考题的例子。给你看看
1. He is old enough to go to school.
He is __________ __________ that __________ __________ go to school.
2. She was so weak that she couldn’t take care of her baby.
She was __________ weak __________ take care of her baby.
（答案：1. so old; he can 2. too; to）
那么在什么情况下三者可以相互转换呢？
一、so…that与too…to的转换
当that引导的从句为否定式且从句主语与主句的主语相同时，so…that可转换为too…to结构；若从句主语与主句的主语不相同时，so…that可转换为too…for sb to结构。例如：
She is so young that she can’t go to school. ＝She is too young to go to school.
The box is so heavy that he can’t carry it. ＝The box is too heavy for him to carry.
二、so…that与enough to的转换
1. 当that引导的从句为肯定式时，若从句主语与主句主语相同时，so…that可转换为enough to结构；若从句主语与主句主语不相同时，so…that可转换为enough for sb to结构。例如：
Xiao Lin is so old that he can go to school. ＝Xiao Lin is old enough to go to school.
The box is so light that he can carry it. ＝The box is light enough for him to carry.
2. 当that引导的从句为否定式时，若从句主语与主句主语相同时，so…that可转换为enough to的否定结构；若从句主语与主句主语不相同时，so…that可转换为enough for sb to的否定结构。同时要注意，转换后的形容词（副词）要用其相应的反义词。例如：
The man is so old that he can’t go to work. ＝The man isn’t young enough to go to work.
The desk is so heavy that I can’t move it. ＝The desk isn’t light enough for me to move.
三、enough to的句式为否定式时，enough to可以转换为too…to结构。但转换后的too…to结构中的形容词（副词）要用其相应的反义词。例如：
He is not old enough to do the work. ＝He is too young to do the work.
The problem is too difficult for me to work out. ＝ The problem isn’t easy enough for me to work out.
改写同义句，每空一词。
1. The book is interesting enough for everybody to read.
The book is __________ interesting __________ everybody likes to read it.
2. The boy is so short that he can’t reach the buttons of the lift.
The boy is __________ short __________ __________ the buttons of the lift.
The boy isn’t __________ __________ __________ __________ the buttons of the lift.
答案：
1. so; that
2. too; to reach; tall enough to reach
怎么样，你听明白了吗？希望可以帮忙！
参考资料：加油！