1) this suit is more expensive than that shirt
-> that shirt is cheaper than this one
2) my sister went to her class late this morning
-> MY SISTER didn't go to her class on time this morning
3) she studied harder than her brother 
-> her brother didn't study as hard as her
4) nam is the most hard - working student in class 8A
-> no students in class 8A as hard  working as Nam
5) we ate this food when we were eight years old
-> we have eaten this food since we were eight years old