Why did people in Europe develop this system called feudalism?

Ineed to do my math homework and i am dumb so i need a smart person to me do math so just say sum if u good at math and i will give u my phone number to me with math

What is the definition of federalism

Which of these would be most useful in studying the effect of germs exchanged between the new and old worlds? a. a graph showing the number of europeans between 1492 and 1600. b. a graph showing the number of native americans between 1492 and 1600. c. a primary source description of the symptoms of an unknown disease affecting native americans in 1492. o d. a primary source description of the symptoms of an unknown disease affecting europeans in 1492.