比我小四岁怎么写不是four years younger than me 书上这么写的可惜是错的和...一样长怎么写 h

比我小四岁 = four years younger than me (对的).比如：He is four years younger than me.
和...一样长 = the same long as,比如：My leg is the same long as yours.
the same ...as = 和...一样
His little dog is thinner than David's.David's = David's dog,为了避免重复使用dog,可省略.

as long as ....

as long as David是个人名没错