Well i think this is right;
If jamie is 3 times Pennys age, and in two years he is twice as old as her i would say she is 2 because; 2 * 3 = 6
2 years later Penny would be 4, because she was 2 at the time. And because Jamie was 6 he will become 8. That means he was three times her age. And then in two years twice his age.
So now Jamie is 8 and Penny is 4.
Hope that helps!