isotopic abundance

KhadijahA's picture

Oxygen(atomic mass 15.9994 amu) has 3 isotopes with masses 15.9949 amu, 16.9993 amu, and 17.9992 amu. The abundance of the last isotope is .204%. Estimate the abundance of the other two isotopes.

I just need to know how to solve it bcuz im confused! thanks