Answer:
View the attached photo, i wrote it roughly but i hope you will understand. And more common bromine is Bromine-79.
Step-by-step explanation:
Remember Atomic number is number of protons OR of electrons.
atomic mass is the number of protons and neutrons.
i got neutrons by subtracting mass number and atomic number.
Bromine-79 is more common because all bromine atoms have 35 protons, this isotope would have 44 neutrons.