Hello, hena!
Ten years ago, Ann's mother was four times older than Ann.
After ten years the mother will be twice as old as Ann.
Find the present age of Ann.
Let = Ann's present age.
Let = mother's present age.
Ten years ago, they were both ten years younger.
. . Their ages were:
We are told that: .
Ten years hence, they are both ten years older.
. . Their ages are:
We are told that: .
Equate [1] and [2]: ,
Therefore, Ann is presently 20 years old (and her mother is 50).