1) Yesterday the temperature was 9°C . Today it's only 6°C
-> Today
2) Jane cooks better than her sister
-> Jane's sister 
3) Nothing is faster than the speed of light
-> The speed of light
4) Jack is younger than his cousin
-> Jack isn't
5) Chinese is much more difficult than English
-> English
6) My father drives more carefully than her father
->
7) Money is less important than good health
->
8) My students are better than your students
->
9) Her parents are younger than my parents 
->
10) All the other books aren't as expensive as this book
->
11) She is taller than her sister
->
12) Minh drives faster than Nam
->