Answer:
The sister's age is 8 and the brother's age is 4
Explanation:
Let's make:
x = age of the brother
y = age of the sister
x - 2 = age of the brother two years ago
y - 2 = age of the sister two years ago
Two years ago, the age of the sister was three times greater than the age of the brother:
y - 2 = 3(x - 2)
Now, the relation doubles:
y = 2x
Substituting in the first equation:
2x - 2 = 3(x - 2)
Operating:
2x - 2 = 3x - 6
Subtracting 3x -2:
2x - 3x = 2 - 6 = -4
Solving:
x = 4
y =2x = 8
The sister's age is 8 and the brother's age is 4