A certain element consists of two stable isotopes.

The first has an atomic mass of 62.9 amu and a percent natural abundance of 69.1 %. The second has an atomic mass of 64.9 amu and a percent natural abundance of 30.9 %.

To calculate the average atomic weight, each exact atomic weight is
multiplied by its percent abundance (expressed as a decimal). Then, add
the results together and round off to an appropriate number of
significant figures.