In your own words, what was feudalism and why did the Europeans embrace it during the Middle Ages?

The feudal society was one organized for war; a central reason for its coming into being was the need for kings and great lords to call forth armies of mounted warriors. This is implicit in the fact that the entire fief-system was based on multiples of knights' fees.

Not in my own words but there ya go

russia because it is the biggest state

equal area projections

equal-area projection. a projection in which regions on the earth's surface that are of equal area are represented as equal.