Question

(b) If the natural abundance of Ag-107 is 51.84%, what is the natural abundance of Ag-109?
48.16 %
(c) If the mass of Ag-107 is 106.905, what is the mass of Ag-109?
108.9 amu

so i got the answers correct but kinda forgot how because it took me a while so do you think you could explain how to get each one?

thanks