We can assign the value "2x" as the amount of money that Amelia which to achieve in twelve years.
So, his initial money is X.
We can try each percent to test if it could double the amount in 12 years.
x+0.06*12years*x=1.72X
x+0.12*12*x=1.44x
x+0.1*12*x=2.2x
x+0.166*12*x=2.992x
Therefore, the answer is 10 percent.
