Question

I just need help with this one question, and then once I know how to do the steps, I think can do the others.
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The average atomic mass of argon is 39.95 u. Natural argon contains three isotopes: Ar-36 (35.967 u), Ar-38 (37.962 u)& Ar-40 (39.962 u). If the isotopic abundance of Ar-36 is 0.006000%, find the isotopic abundances of the other two isotopes.

Thanks for your help.
~Lucy

Answer 1

average*100= sum of weights*abundance
= 35.967*.006 + 37.962*P + 39.962*(100-P-.006)

solve for the abundance for Ar38 (P), then the abundance of Ar39 (100-P-.006)

Answer 2

Thanks for your help, but I tried and I still couldn't get the right answer.
I need help solving for P. . .