Answer: Helen is 8 years old.
Step-by-step explanation:
Given: Helen’s age is a multiple of 4.
i.e. Choices for Helen’s age = 4, 8 , 16, ...
Helen’s older brother is now 19.
That means Helen's age < 19
Choices for Helen's age left = 4, 8, 16
Next year it’ll be a multiple of 3.
That is only possible if Helen's age = 8
Because next year her age = 8+1 = 9 years which is divisible by 3.
Hence, Helen is 8 years old.
