To find the answer, we have to set up an equation:
Let the weeks be x.
The amount Ramona has after x week:8+1(x)
The amount Claire has after x week:12+3(x) or 2[8+1(x)], as written in the question above.
12+3(x) = 2[8+1(x)]
12+3x = 16+2x
3x-2x = 16-12
x = 4
Therefore, the answer is 4 weeks.
Hope it helps!