Answer:
The information given is not enough to determine their ages explicitly, so, here their ages are given in terms of Anna's age, which is the best that could be determined.
Anna's age = x years
Robert's age = (x - 11) years
Sara's age = (x - 9) years
David's age = (x - 1) years
Step-by-step explanation:
Let Anna be x years old.
Anna's age = x
Because Anna is 11 years older than Robert, we can say Robert's age is Anna's age minus 11.
Robert = x - 11
But Robert is 2 years younger than Sara, we can say Sara's age is Robert's age plus 2
Sara = (x - 11) + 2
= x - 9
David is 8 years older than Sara, we can say David's age is Sara's age plus 8.
David = (x - 9) + 8
= x - 1
