Okay so to find the average atomic mass of copper in this location, you want to take the percentage of abundance of an isotope and multiply (in decimal form) that by it's atomic mass, then you would add that with the product of the % of abundance of the other isotope times it's atomic mass.
(Side Note: Isotopes are atoms of the element that have the SAME number of protons but different number of neutrons, so they have different mass numbers. Also average atomic mass is the average of all the isotopes in an element - this number is the one that is shown on the periodic table of elements, not mass number).
Let me show you how to do this..
For the isoptope 63Cu I will first need to convert it's percentage of abundance into a decimal, because we don't use the percentage to multiply. 69.97% -> 0.6997. Now I am going to take it's atomic mass 62.9300 and multiply that by 0.6997.
62.9300*0.6997=44.0321
Now we still need to find calculate this for the isotope 65Cu. To convert 31.03% to a decimal I will just move the decimal point two places to the left, to get 0.3103.
So I am going to take this and multiply it by 64.9200 the atomic mass of the isotope 65Cu.
64.9200*0.3103=20.1447
Add the two of these to get the average atomic mass..
20.1447 + 44.0321=64.1768
