As shown +
A Sample of propane C3H8, was completely
burned in air at StP. The reaction occured
C₂ Hg + O₂ CO₂ + H₂O
If 3 mol of CO2
were produced and
all the carbon in the co2 came from
the propane, what was the mass of
the propane Sample ?

c2 is a Air that you break

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.