Hydrate problems

[drablnd]

I am having some problems understanding how to solve hydrate problems. Below are two of the problems my professor had on our last quiz

1. A student is running an experiment in which 41.3 grams of magnesium sulfate is needed, but the only jar of reagent in the lab is labelled magnesium sulfate heptahydrate. How many grams of the hydrate must the student weigh out in order to get the desired amount of the anhydrous compound?

2. It is often possible to change a hydrate into an anhydrous compound by heating it to drive off the water (dehydration).
A 87.2 gram sample of a hydrate of MgI₂ was heated thoroughly in a porcelain crucible, until its weight remained constant. After heating, 57.4 grams of the anhydrous compound remained. What is the formula of the hydrate?

Can someone explain how to solve these? please and thank you!