What element provides strength to the exoskeleton of Clams and oysters

Does anyone know a lot about how to: - calculate mass of magnesium metal - calculate the actual yield of magnesium oxide - calculate the theoretical yield of mgo - calculate the percent yield of mgo - determine the percent yield of mgo - determine the average percent yield of mgo i had to do an online lab and its asking these questions but i have no idea where to start or how to be able to find these things. i can post the chart of the data from the lab or if you can tell me exactly how i can find each.

In pea plants, the allele for tallness (t) is dominant to the allele for shortness (t). in the cross between a tall pea plant and a short pea plant shown below, what is the probability that the resulting offspring will be tall? whats the percent

Which best explains why an iceberg floats?