Answer:
S = x+y+9
Step-by-step explanation:
Age of Anna is x years and age of her sister is y years old.
3 years later,
Age of Anna = x+3
Age of her sister = y +3
Sum of their ages in 3 years will be :
S = x+3+y+3
S = x+y+9
Hence, this is the required solution.
