Sure! Here’s a rewritten version of the sentences you provided:

23. Lan is more intelligent than her sister.
> Lan's sister is not as intelligent as she is.

24. I can't cook as well as my mother.
> My mother is a better cook than I am.

25. He doesn’t play tennis as well as his father.
> His father plays tennis better than he does.

26. I didn’t spend as much money as you.
> You spent more money than I did.

27. I don't think this book is as expensive as it is.
> This book isn't as expensive as it seems.

28. He is the tallest boy in his class.
> No one in his class is taller than he is.

29. This is the most interesting film of all.
> No other films are as interesting as this one.

30. No cars in the world are more expensive than Japanese ones.
> Japanese cars are more affordable than others.

31. This exercise is easier than that one.
> That exercise is not as easy as this one.

32. John drives more carefully than Jack does.
> Jack does not drive as carefully as John.

33. No one in the group plays better than he.
> He plays better than anyone in the group.

34. My brother runs faster than me.
> I don’t run as fast as my brother.

35. Your car doesn't give as much trouble as mine.
> My car gives more trouble than yours.

36. Lan is the youngest of the three sisters.
> Lan has two older sisters.

37. No one in my class learns better than Ba.
> Ba learns better than anyone in my class.

38. Do you have a better stove than this?
> Is this stove not as good as yours?

39. No one in the group is younger than Hoa.
> Hoa is the youngest in the group.

40. I don’t eat as much as my father.
> My father eats more than I do.

41. I have more books than you.
> You have fewer books than I do.

42. He doesn't work as hard as you.
> You work harder than he does.

43. She has more money than I.
> I have less money than she does.

44. He drinks more carefully than I do.
> I don’t drink as carefully as he does.