Lithium has two isotopes.
li-6 and li-7.
li-6 mass = 6.015121amu
li-7 mass = 7.016003amu
lithium mass = 6.94049amu

what is percent abundance of li-6?

i know that there is an equation:
6.9409 = (% abundance li-6 * weight of li-6) + (% abundance li-7 * weight of li-7)

i don't know how to use it.

One way in which the useful metal copper is produced is by dissolving the mineral azurite, which contains copper(ii) carbonate, in concentrated sulfuric acid. the sulfuric acid reacts with the copper(ii) carbonate to produce a blue solution of copper(ii) sulfate. scrap iron is then added to this solution, and pure copper metal precipitates out because of the following chemical reaction: (s) (aq) (s) (aq) suppose an industrial quality-control chemist analyzes a sample from a copper processing plant in the following way. he adds powdered iron to a copper(ii) sulfate sample from the plant until no more copper will precipitate. he then washes, dries, and weighs the precipitate, and finds that it has a mass of .