Chemistry
posted by Liz .
I am supposed to find the percent abundancies of two isotopes. I am given the masses of both isotopes, along with the atomic mass. (This is a fictional element with only those two isotopes.) I am not given percentages for either isotope... how do I solve this?

Well, if the Percent of A is A, then the percent of B is 1A (decimal percents.)
Then
avgatomicmass=massA*precentA + massB(1percentA)
solve for percent of A.