If he is 4 now is in 10 years he will be 14 and if you multiply that by 2 you get 28 which means in 10 years Marie will be 28 so that means if you take away 10 the answer should be 18 but that isn't there but that's how I would work it out.
The atomic number is defined by the number of protons in an element. An element is defined by the number of protons the nucleus contains and doesn't have anything to do with how many isotopes the element has. Carbon always has an atomic number of 6 and uranium always has an atomic number of 92. I GOTCHU BROOOO GET THATS A BUDDY
