Naturally occurring boron is 80.20% boron-11 (atomic mass 11.01 amu) and 19.80% of some other isotope. What must the atomic mass of this second isotope be in order to account for the 10.81 amu average atomic mass of boron?

Question

Ferredoxin4 · Answer

remember the formula I showed you earlier?
Use the same thing but solve it like algebra. this time the mass number of the second isotope is unkown

10.81 = (0.8020 * 11.01) + ( 0.1980x)
solve for x

I think you do that algebra if you're in chem