Xiaohua is always four years older than Xiaoming, which becomes a question of harmony and difference!
(50-4)÷2=23
23- 14=9 years
Nine years later, Xiaoming and Xiaohua are 50 years old.
Xiaoying is 7 years old and Xiaoying's father is 35 years old. How old was Xiaoying, when his father was three times older than Xiaoying?
Dad is always 28 years older than Xiaoying, which becomes a problem of difference!
28÷(3- 1)= 14 years old.
When Xiaoying 14 years old, her father was three times as old as Xiaoying.
Sister is 30 years old and brother 16 years old. A few years ago, my sister was three times as old as my brother.
The elder sister is always older than the younger brother 14 years old, which becomes the problem of difference times!
14(3- 1)= 7 years old.
16-7=9 years
Nine years ago, my sister was three times as old as my brother.