Answer:
The average atomic mass is 79.91 amu.
Step-by-step explanation:
Since
Atomic mass can be find by Multiplying the relative abundance of each isotope by its atomic mass, then add them together to get the atomic mass of the element.
so
Atomic mass = (0.5069)(78.92 amu) + (0.4931)(80.92 amu)
=79.91 amu
So the Atomic mass of the bromine is 79.91amu.