A boy is 6 years older than his sister. In 3 years time he will be twice her age. What are their pre

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A boy is 6 years older than his sister. In 3 years time he will be twice her age. What are their present ages?

Let b be the boy's age and s be his sister's age. We're given two equations:

1. b = s + 6
2. b + 3 = 2(s + 3)

Plug in (1) to (2):
(s + 6) + 3 = 2(s + 3)
s + 9 = 2s + 6

Plugging this equation into our search engine, we get:
s = 3

We plug s = 3 into Equation (1) to get the boy's age (b):
b = 3 + 6
b = 9