Why were the spanish so successful in subjugating the natives of americas?

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69

in which two ways were the northeast woodland indians and the southeast indians similar? both collaborated to form the iroquois confederacy. both cultivated the crops of corn, beans, and squash. both lived in rich environments of swamps and rivers. both lived in tree-bark dwellings called wigwams. both expected men to hunt, while women farmed.