I believe it would be 1.660539040 × 10−24 gram.
We know that Weighted atomic mass of Element is Calculated based upon their existence of isotopes and the Relative abundance of these isotopes.
Given that the Element X is Composed of :
Isotope Relative abundance Atomic Mass
⁵⁵X 70% 55
⁵⁶X 20% 56
⁵⁷X 10% 57
Weighted Atomic Mass of Element X :
= (0.70)(55) + (0.20)(56) + (0.10)(57)
= 38.50 + 11.2 + 5.70
= 55.4
So, the Weighted Atomic Mass of Element X is 55.4
Like A B C D or like a mailed letter
Molar mass Mg = 24.3 g/mol
1 mole mg ------------ 24.3 g
?? moles mg --------- 4.75 g
4.75 x 1 / 24.3 => 0.195 moles of Mg
hope this helps!