Answer:
5 years
Step-by-step explanation:
1. if able's age is x, then his sister's is x-4, and his brother's is 2x
2. if these sum to 32, then we can formulate the equation x+(x-4)+2x=32
3. now solve for x, 4x-4=32, 4x=36, x=9
4. if able's sister is x-4 years old, she is 9-4, or 5 years old
