Question

Im confused there is an example in image 1
i dont know how im too lazy to do it

Answer 1

Atomic weight =

(AMU*Abundance%)+(AMU*Abundance%)

so thats

(62.9296*69.15/100)+(64.9278*30.85/100)

43.5158184+20.0302263

≈63.55 amu

hope i helped