Girl is 18 years old and her brother is a third her age. when the girl is 36, what will be the age of her brother? enter a numerical value only.

Hey,
If you mean brother's age is 1/3 of her age, than he is 6. When 18 year passes and the girl becomes 36, he will become 6 + 18 = 24.
If you mean brother's age is threefold of her age, than now it's 54. When 18 year passes and she becomes 36, he will become 54 + 18 = 72

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