The element X has two naturally occuring isotopes.  The mass…

The element X has two naturally occuring isotopes.  The masses (amu) and % abundances of the isotopes are given in the table below:   Isotope      Abundance (%)       Mass (amu)     79X 50.7 78.9183 81X 49.3 80.9163 What is the average atomic mass (amu) of element X?