What is the average atomic mass of a sample containing three Lithium-6 atoms and two Lithium-7 atoms?

Ineed with my science work! it’s due tomorrow!

During chemistry class, carl performed several lab tests on two white solids. the results of three tests are seen in the data table. based on this data, carl has concluded that substance b must have bonds.

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.