A solution of CaCl2 in water forms a mixture that is 28.5% calcium chloride by mass. If the total mass of the mixture is 729.5 g, what masses of CaCl2 and water were used

it's c (engineer's do their work with mechanical stuff not on any living being)

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.