Answer:
[tex]\boxed {\boxed {\sf 55.76756 \ amu}}[/tex]
Explanation:
The average atomic mass is the sum of the product of the given masses and their abundances. We have to complete two steps for each isotope, then add all the products together.
Fe-54
Convert the percent abundance to a decimal by dividing by 100.
Multiply the abundance as a decimal by the mass number. This is the number after the element in the isotope symbol (54 amu).
Fe-56
Convert the percent to a decimal.
Multiply the decimal by the mass number (56 amu).
Fe-58
Convert the percent to a decimal.
Multiply by the mass number (58 amu).
Average Atomic Mass
Add all the products together to find the average atomic mass.
The average atomic mass given the percent abundance is 55.7656 atomic mass units.