1) He is taller than his sister. – His sister is shorter than he is/him.
2) Ann dresses more smartly than Erika. – Emily dresses less smartly than Ann. (наверное, вместо Emily должна быть все же Erika)
3) Tom is noisier than his brothers. – His brothers aren’t noisier than him.
4) If you work more, you will earn more. – The more you work, the more you will earn.
5) She is the quickest runner of all. – She is quicker than any other runner. No other runner is as quick as she is/her.
6) If you try harder, you will do better. – The harder you try, the better you will do.
7) Wealth is not as precious as health. – Health is more precious than wealth.
8) Ann studies less diligently than she did in the past. Ann does not study as diligently as in the past.
9) He is a terrible driver. – He drives terribly.
10) Tom has got the same number of books as John. – John has got as many books as Tom.
11) She hasn’t made as many mistakes as last time. – She has made fewer mistakes than last time.
12) No one else on the team plays better than he does. – He plays best of all on the team.