How are heterogeneous mixtures and solutions different?

Both are considered mixtures - that is, they are made up of two or more pure substances. ... A heterogeneous mixture appears to be made of different substances. A solution appears the same throughout. In the fluid phase (gas or liquid, or any combination of those) a solution is transparent (thought not colourless).

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.