First, we need to find her current age. If she was 12 years old 3 years ago, her current age is 12 + 3 which is 15. If the ratio of Sarah's age to Keisha's age is 4:5 (Sarah's age is the 4 and Keisha's age is the 5).
If we take 15 and divide that by 5 (her ratio), then you get 3. Now multiply 3 by 4 to find Sarah's age. We get 12. Nine years from now, her age is 12 + 9 which is 21.
There is the answer. Sarah's age in 9 years is 21 years old. I hope this helps.
