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how should measurements and calculations be reported to reflect uncertainty?

See below  

Step-by-step explanation:

Measurements

Every measurement must be reported with the correct number of significant figures.

Calculations

The results calculated from a measurement are at least as uncertain as the measurement itself.

You must follow the correct significant figure rules for

You must follow the correct rules for rounding the results of your calculations.

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.